Because companies don't need to and scale eats everything. Unfortunately, we're in such a winner-take-all environment that anyone hoping to compete with YouTube is starting at a huge loss.

If Peertube takes off (and I hope it does) it would likely be on the back of something that's expressly anti-status-quo. (Which doesn't mean it couldn't be a company per se, but I feel like would have to wear "We are the anti-Youtube" on its sleeve.)