To play devil's advocate for a minute, one of the downsides of people hosting their own files for use on anything social is that individual hosting decays. If you read a forum from five or ten years ago, it's quite normal to see broken image links all over the place. My own self-hosting has changed domain, though for the time being I've retained the old one. If a site wants to preserve a professional image and avoid brokenness, it makes sense for them to take control of media hosting. Of course, it would be nice if they did it better, and as a user you're stuck handing over control to a faceless corporation - as you are with all the rest of your data.