Because any of those are even close to competitors...there are 2 billion youtube users (80% of internet users).

Posting this reply here since the site says Im posting too fast at a lightspeed rate of 3 comments for the day:

I just dont agree with you that there is a "healthy marketplace" by all metrics youtube has a monopoly on video streaming. For instance Vimeo has 1.5 million subscribers...compared to 2000 million for youtube. Thats .075%.