Building a following on Steemit maybe much, much more profitable over the long-run, as every follower you get, or at least some percentage of your following, will be giving you upvotes for years to come.
That is not the case with Youtube, FB & Twitter, where your followers don't get compensated for commenting and viewing your material, and they are also forced to watch ads so you can make money.
Steemit makes it financially beneficial for both content creators and viewers/commenters!! Bid difference right there!