About decentralized platform for videos, check out what @justineh wrote about this subject. It's really interesting.

But as for no known content creator caring about steem I can list a few probable reasons:

1 - the user interface sucks. It can't attract "normal" users like other social media because its too complicated
2 - steem have an old fame of being a scam, because of all the ninja mine that happened at the begining of the blockchain.
3 - those with steem power/influence are too busy circle jerking each other to bother to look outside.
4 - There is no real incentive to abandon well stablished and fully functional platforms to join steem
5 - steem inc./ned have no idea what they are doing
6 - a big part of the funds are being redirected to stuff that bring dubious value
7 - there is always somebody coming up with "great" ideas, like the @sbdpotato that direct attention and rewards to totally useless projects
8 - most of the community sucks, it's hard to find interesting things to read, because there is not many interesting creators.

I could add a few more, but I have to go to sleep now...