How does Google play store list apps?

Why does Amazon store contain much fewer apps than the Google Play store?

• Is there much difference between an Android app on the Amazon store vs google play? I am wondering why there are so few apps compared to Google Play. I mean, if you've spent the time to develop a whole android app, surely it shouldn't be much more trouble to just upload it to both stores. Why wouldn't all Android apps be in both (plus even Samsung and other stores) Or is there actually some technical work that needs to be done? Like have to re-compile or something? What are some of the things that must be done to get your Google play app in the Amazon store?

• Answer:

  Virtually all mainline versions of Android will have access to the Google Play Market, but only those users that follow the instructions below will have access to the Amazon App Store. https://www.amazon.com/gp/feature.html/192-2910637-3961300?ie=UTF8&docId=1000626391 This isn't terribly difficult, but there isn't a lot of motivation for most users to do this.  This means the biggest reason app developers want to be on the Amazon App Store is to target Amazon Kindle devices which don't have access to the Google Play Market without going through a significant bit of hacking which voids the warranty. http://reviews.cnet.co.uk/ipad-and-tablets/how-to-get-the-google-play-store-on-the-kindle-fire-hd-50010454/ So, for those developers targeting Kindles the Amazon version of Android is quite different from the mainline and often the kernel is much older.  In addition many libraries that app developers depend on either don't exist on the Amazon App Store or a different version than the one on the Google Play Market.  A good example of this is Adobe Air.  Perhaps more importantly, the kinds of consumers that buy Kindles are different from consumers of mainline Android. In short it can be both technical and business reasons that keep app developers that are already on the Google Play Market out of the Amazon App Store.