I think it has to do with the social scalability. There is an incentive to provide valuable content plus to me it is amazing how everyone here helps each other with questions you may have whether we are quote on quote friends or not.

There was another social network called TSU, I don't know if you heard about it and ended up going dark. I gave it a try but most of the post there didn't seem to be quality posts like you find here plus it was not decentralized and not searchable by search engines I think.

Let's hope the steemit community keeps growing to increase valuable content.