Except of a very subjective (repelling) associations with Facebook, what steemit supports and facebook doesn't is the quality of contents (oh sure Facebook doesn't).
On facebook every vote is eseentially worth the same, thus you just need to hit the BIGGEST audience, no mention of quality - After all, Bill Gate's like on facebook is worth the same as mine.
Hence many people retreating to pop culture and pop topics.
Plus, there is no downvoting for posting crap. Controversial is good, because it brings voters. And votes can only be good or none.
To an extent same for youtube - where downvotes can be switched off by turning off the ability to comment and vote. At least on steemit there is a possibility of real criticism and you don't get paid unless someone sees some potential in you :)
That are some very good points.
They would need to change the current system quite a lot and I dont think they really want to do that, also.