Personally I think it's because once you have your post paid out you can neither edit it or delete it which is a very tricky issue to many bloggers.
Plus the current steem price is low and the future is unpredictable, so many folks are having a tingling fear of losing their cash in this platform.
Plus steemit is yet to face malssive competition from other platforms that pay folks to monetize their content.
I believe that it is now possible to edit a post after seven days, Well at least with Steempeak.
I agree that there is a lack of competition but that should all change with Voice on EOS coming in February. It will be a big challenge for Steem to stay ahead but it does have first mover advantage.
first mover advantage is temporary. If things don't evolve, it doesn't matter in the long run.