Flickr has excellent organisation features (tags, sets, collections, Organizr, map, search, etc.) and I like having my photos organised. Because it's on the web and not a desktop app, I have access to my well-organised photo library from anywhere in the world. And once you've put some investment into organising your photos on any software, that's a strong lock-in. I suspect this applies for a significant percentage of users.

The main purpose of Flickr for me has become sharing photos with family and friends, and seeing updates from people I know, and from people who take interesting photos. I also enjoy getting comments from strangers, and serendipitous discoveries.

I also want my photos to exist as part of the web, and not permanently inside a walled garden (such as Facebook). I care about the future of my photo library in years to come, and I think Flickr offers a better guarantee of that than competing services.

Flickr, like all well-designed software, is extremely versatile in what you can use it for, so I think you'll find there is a multitude of reasons why people stay loyal to it.

There is no limit to the number of pictures you can upload to Flickr.

SHORT ANSWER:

NOT ANYMORE…

In my opinion: Unless you spend a LOT of time promoting only your most amazing photos by participating in many Flickr user groups and linking elsewhere, few will ever see or react to anything you post. That’s just how it’s set up now.

I’ve had 1 million Flickr views since 2010… 10,000+ photos. A recent upload received 4,586 views and 82 favorites. Not bad, but I’ve gotten up to 22,000 views in one day elsewhere with a tiny fraction of the time spent on Flickr.

This could change soon. Terms and conditions routinely do on Flickr. A little backstory:

2013: Yahoo/Flickr CEO Marissa Mayer famously stated when announcing 1TB of free Flickr space: “There’s no such thing as Flickr Pro today because [with so many people taking photographs] there’s really no such thing as professional photographers anymore.” (link to story)

2018: Flickr, now owned by SmugMug, requires $50 per year for the “Pro Plan” or they delete all but each free user’s newest 1,000 photos in February 2019. (Link to the Flickr announcement)

In my personal opinion, this reversal sets a dangerous precedent. Other sites could follow suit. Shorter deadlines. Higher ransoms.

What do users get for $50 per year on Flickr?

1. An ad-free experience—something I already enjoy for free using Firefox.

2. NEW “worry-free” backup. Whatever that means. They don’t say. I never took Flickr backup seriously because they don’t allow RAW files and automatically post each folder publicly as an album with the same title as the folder. Tedious to organize. Not nearly enough options. Nobody I know wants every image file they back up to be available for public viewing. And I’ve noticed a massive drop in the upload speed of high-resolution photo batches since the 2013 Flickr overhaul. And around 2016, these slow uploads also routinely error out and fail altogether so I don’t post much anymore.

3. The community. Most groups require users to comment on 3-5 other people’s pictures for each one they submit. Bots determine compliance and failure to post enough comments results in automated banning from the group. And Flickr currently suppresses all user’s exposure by limiting the number of groups they can submit a photo to.

Conclusion: You might be dumping your work into a fruitless black hole. Millions of beautiful photos linger in obscurity and SmugMug threatens to delete most of them in February.

2/22/19 UPDATE:

SMUGMUG HAS SET FLICKR TO SELF-DESTRUCT.

• Flickr messages encourage users to to avoid deletion of all but their newest 1,000 images by switching copyright settings to “creative commons” .
• Image uploading process still fails with large batches of full-resolution JPEGS—at the last minute—after much time spent uploading, labeling, and tagging. Pathetic…
• Paid “Pro Plan” users are now limited to 60 user groups per image. To me, that translates as, “don’t bother promoting your photos on Flickr.”

And customer service ignored my message.

I will NOT be renewing…

Steps
1. Go to http://Flickr.com.

If you are logged in, it will take you to your 'Home' page. If not, sign in.

Click on "Group".

2. From Groups, scroll down to Create a New Group.

3. Choose the type of group setting (private, public (invitation only), or public).

This article shows you how to create a public group.

4. Name your group and select the Group Safety Level (whether it is age-restricted (18+) or not).

Try to use a group name that would make sense to people searching for your interest or for the types of photos you'll be grouping in it. Press Next.

5. Click on "Groups" above to see your groups.

Your new group should now appear. Go to your group's Administration page (click on the tab Administration located under your group's name) and make any needed administrative type decisions.

6. Control the viewing level of those visiting the group.

Under Privacy you can select what you want to display to non-members.

7. Select what you want the different levels of members to be called (under Membership).

8. Start making your group interesting.

Click on Add Something? located on the group home page. This will take you to your photostream and you can start selecting photos from there for the group. Up to six photos can be added at a time and you can use the Search box to find relevant tags on your photos. Look at the drop-down box under the words Your Photostream; it will show you that photos can be retrieved from:

All your items

Your sets

Photos uploaded on a certain date

Your groups

Geotagged or non- geotagged items.

According to this Yahoo Flickr advertising pitch page there are currently 51 million registered Flickr members. http://advertising.yahoo.com/media-kit/flickr.html

Yahoo further cites "24.8 million unique U.S. visitors (nearly 80 million worldwide) spending an average of 2.7 minutes per vist to the site. Not all of these visitors would have accounts. Some can be just visiting the site, looking for stock photography, or just browsing. Yahoo doesn't disclose active accounts, but if I had to just make a wild guess I'd speculate somewhere between 10-20 million -- and I could totally be wrong on that.

Both compete.com and comScore show that traffic has declined significantly in the past year at flickr.

You could share them in a group you belong to

You could create your own group and add your friends to it

You could share using the share button in social networks

You could ask people to suscribe to your feed (various feed available) at Flickr Services

Finally, you could use IFTTT recipies to sync/automatize your activity and share it to your friends/audience

• Flickr is a showcase for talented amateur and professional photographers: in this sense it can be compared to 500px, though flickr allows for immediate access to 1tb of storage and unlimited daily upload for free accounts whereas 500px limits the upload amount depending on the kind of account and does the same regarding storage.
• Flickr is a place to backup all your photos: in this sense flickr can be compared with google photos/microsoft one drive/dropbox/amazon's etc. Still, flickr provides more storage for free and a photo community behind.
• Flickr is a place to get photos from: In this sense, flickr poses a major alternative to most stock photography sites like shutterstock, etc. Creative commons, share alike, etc.
• Flickr is a marketplace: in this sense Flickr can be compared to getty images or 500 px.
• Flickr is many other things (a place to get prints online, etc.) but for that you can read about flickr at wikipedia