Several tried. Nothing as elaborate as cross dissemination, federation or whatever. But at least 5 to 10 years ago it proved to be almost impossible. Platforms like Rooster teeth, which was 100% subscription based, I think never broke even and still relied on YT ads for the majority of the revenue. Some big and small channels tried to at least just catalog, archive and serve their own videos and the costs still became astronomical really fast. Whenever you see one of those very old channels, most of them don’t conserve copies, let alone original source footage of their entire material. Everyone just delete their videos once they’ve been on YouTube for a month or so now, and they have to download their own videos when they want to reuse old footage.

Storage is cheap today, yes, but video really eats storage at an alarming rate. Specially now that 4k is the standard. So you have to reuse storage over and over. Transcoding is also really fast and optimized with modern algorithms, but it takes specialized graphical cards and data centers charge a premium to use servers with such capacities. Self hosting will never be able to satisfy a moderate demand. Get anything above 100 users simultaneously transcoding videos and a non-specialized server will halt to a grind just on IO calls to hard drives alone.

Once you consider all those factors it is obvious why YouTube is such a miracle.