Massive up front investment. Millions of dollars of hardware, distributed to be close to end users to minimize latency, all with their own redundant internet connections.
Petabyte level storage- that’s thousands of terabytes. Video storage takes up a lot of space, and storage drives fail. For every piece of equipment you have to buy a second one to run in parallel, that way if one fails the other can keep the system running. Oh, and you need a third so you can replace the one that failed.
Hosting in general is a very high investment prospect. You can do it Inexpensively using something like plex, but that isn’t very scalable.