Why should Apple merge iOS and Mac OS?

iOS and OSX are not really different OSes. They are essentially the same technology. There is a lot of code is in common, and and in most cases, the Cocoa programming APIs are almost identical. They are two branches of the same OS and each branch serves a different design goal. It is likely that a third branch will start appearing in embedded devices (like the Airport base station) replacing NetBSD. Maintaining both branches is not a problem. It should be noted that new OS technologies (ARC / Grand Central Dispatch) and so on are incorporated into both OSes simultaneously, iOS was deliberately branched from OSX - because a) iOS devices have a fundamentally different user interface (touchscreen) b) iOS devices do not need the bulky historical cruft associated with desktop apps. Apple should not merge until these reasons cease to apply. For the foreseeable future, I think there will remain reasons to provide a conventional desktop OS - based around a touchpad and keyboard interface with support for legacy desktop applications.   -  Alongside a touch-screen OS which is streamlined around being a appliance style personal computer. What is likely is that great features from iOS will materialise in OS X and vice versa. But don't confuse that with merging.

Just answered to , so copy-pasting part of my answer there in this question. Let us look at things the other way first: what would motivate Apple to keep OS X and iOS separated? iMacs and MacBooks (and more generally, desktops and laptops) have uses that iPads / iPhones / other future iOS devises don't / won't have. What would be these uses? As far as I can tell, the main uses of PCs would be word / data processing, Internet surfing, programming, gaming, all sorts of graphic, audio, video production. Now we all know that iOS devices are very good for Internet surfing (and offering an equal if not better experience than Internet browsing on PCs), are progressively turning into advanced gaming machines, and that, for the rest, if you remove the lack of keyboard (critical for data processing or programming), it currently does the job quite well. Eventually, anything that you do on a PC could end up being done on a tablet (granted that a keyboard is available for some uses). Consequently, this argument is void. The future of desktops / laptops is completely separate from the future of tablets and phones. We just saw that possible uses of both devices can be exactly the same in the near future. Now, today, a PC offers advanced multitasking, extreme flexibility in what you can download and how you can customize your programs, files and folders, and eventually how exactly you want to customize your OS. iPhones and iPads are far from offering that today. Nonetheless, Apple is coming today with the Gatekeeper functionality (http://www.apple.com/macosx/moun...), and is about to virtually limit download flexibility for a lot of people. Power users will not like it (hence not use it), and would not appreciate to have no control on what they really can download on their device (which is the case on iOS devices). The question then is: does Apple what its Mac line to become more closed and "safer"? I would say it does. Might Apple lose a lot of current Mac customers because of that? Possibly, but who cares? The real cash cow is not here for Apple, as this graph shows: So Apple could really go all the way, limit the download pipe to Apple-approved developers, and keep a significant amount of users, + get plenty of new ones who would like this idea of safety! As for the rest, advanced fast multitasting is definitely what iOS is looking into, and customization of the OS, aside from power users (who would be able to do it anyway), nobody cares. So, in terms of technical potential, mobile devices will keep catching up with desktops and laptops. In terms of the flexibility / customization potential that the latter have, people will end up not caring, or favoring their safety and peace of mind. Which is super cool for Apple. Void. Offering the same OS for all the Apple devices would make them too similar and kill cross-selling opportunities. Well, that doesn't seem to be in Apple's DNA to sacrifice the potential of a new product because it would cannibalize an existing one. However, Apple wants us to have an "iExperience" all the way (iCloud is suggesting it more and more, and the upcoming iTV will strengthen this even more). Hence, it's important for Apple to have a large amount of customers with at least two devices. When we look at the two-device combinations possible by choosing among iMac, MacBook, iPad and iPhone, we already see a lot of redundancy. Yet people buy multiple products from Apple and love it that way. Now, if tomorrow the MacBook Air ships with the same OS as the iPad, will I be less incline than today to buy one product only or both of them? Maybe I will tend to favor the Air more (or the iPad more), but in the end, it makes no difference, Apple will still increase their bottom line. So I wouldn't care much about that argument if I were Apple. Void. From a technical perspective, shifting from OS X to iOS would be a pain for most current Mac models. That's possible, I don't have a technical enough background to answer this in detail. But, merging both OSes is not supposed to be a one-step process (and assuming it will eventually happen , it has already started with Lion and the upcoming Mountain Lion). And in terms of hardware, Apple could clearly start shipping MacBooks and iMacs which could support such a shift, two, three, four years ahead of a total merger of the OSes, and make the retro-compatibility possible only for these devices. That wouldn't shock anyone, would it? Hence, void. That's all I see. If anyone sees additional arguments, please feel free to comment and I will edit. Now, I see a lot of elements in favor of this merger, which actually fit into one single argument: the iExperience, all the way. Apple is today the world biggest company in terms of capitalization, it holds a gigantic amount of money in the bank, yet, it will never own a Google-kinda-market-share for phones and certainly not for PCs. In order to protect its gigantic App Store and keep it that way, to popularize its iMessage and other iGadgets, it needs both breadth and depth of reach. A closed market, with each single user connected to each other through multiple devices is the strategy. And once you are locked in, attrition is obviously lower than it is with other phone, tablet or PC manufacturer. So, by offering a seamless, similar experience via all the Apple devices, it will guarantee that not only you might need / buy more devices, you would interact more between them and have more interaction opportunities with the other Apple device owners. I can already see myself Airplaying from my Mac to my iTV to my iPhone, and imagine how important iMessage will be to me and my friends within a few months (and it's already quite a lot!). On top of it, the future, the mainstream future, of PCs, is definitely a more ergonomic and simple experience. OS X is all that, but iOS is too, and is more praised for it. So for me, there's no doubt. OS X will become iOS. Sooner than we think! And it is all in Apple's interest.

OSX is for laptop/desktop.  The paradigm shift Apple is being a first-mover in is the idea that the laptop/desktop is now just another device, not the center of your personal computing ecosystem.  It therefore makes absolute sense that all these 'devices' run on the same OS, but no distinction.  All the software power will be managed in the 'cloud'. What other company is even close to replicating a similar paradigm shift?  Yeah, I can't think of one either.

They shouldn't. At least as of now when Mac is not getting touch input. Both systems have different input methods, different specs, different screen sizes and different causes of use. Therefore a different OS for both makes perfect sense. One might think that Apple is merging iOS with OS X with Lion, Mountain Lion and Mavericks. But Apple is being intelligent as always and merging only those features which will be useful for Mac. For example, the multi touch gestures. I use a lot of them and it gets really handy with these gestures. If at a some point Apple decide to make something like "Mac Touch" then it makes some sense merging the OS'.