I have at least three possible theories:

  - Flickr was slow.  I can't stand slow services and over time I tend to avoid these services even though I want to use them.

  - I think there was an uptick in photography for me during the decade when digital cameras went from "meh" to "wow".  And then suddenly the world was flooded by meaningless beauty when everyone had a good camera (including on their phones) and a bunch of filters.

  - I think social websites filled people's need to tell their story.  Flickr, to some degree did that for many people.  Albeit in a more abstracted, indirect way.  With social media there is more immediacty and there is an ephemeral quality to how you communicate.