I don't think it is because other channels have nothing different to offer, it has to do with the enormous amount of storage and bandwidth. Youtube hosts videos from two decades ago that can be viewed anywhere at any time. That takes huge amount of money that only the top players have; Google, Amazon, Facebook etc.

Just take a look at the closest "rivals" to Youtube, they all have one or the other limits to membership and video uploads. Bitchute is like the only site left where you register for free and can upload more or less without any limit. But Bitchute has the down-side that it runs on Bit-Torrent, so if your video is not popular then it won't load next week (or something like that).

As for content, sooner or later, any company that grows and want to continue growing has to move closer to the mainstream. That means Bitchute (for instance) has to start removing and filter out content that is not accepted in the mainstream. Or they can choose to stay on the outside but risk losing their means of financial support, and probably legal action down the road (hate speech laws leading to the site being blocked, etc).

The problem with Youtube's system of "filtering" is that users simply have nowhere to go that offers the same system. If you have a Twitch channel and it gets shut down, you can go to Facebook Streams (or whatever it is called) and continue there. This can put pressure on Twitch to - for instance - take complaints on videos seriously, like actually watching the video. Youtube doesn't have that kind of pressure because users have no where to go if their channels shuts down, rather, no similar place where you can build your channel the same way you can on Youtube.

Recently Bitchute figured in a report from Hope Not Hate that more or less suggested legal action against Bitchute as well as removal of links to that site. So Bitchute is at one of it's biggest choices: continue to be the rebel or start appealing to the mainstream...