Specialization is at the heart of increasing productivity. Let's say a given person makes awesome travel videos. If that person can find a way to broadcast and monetize those videos with YouTube, Vimeo, or whatever, that almost certainly makes more sense than devoting their time to maintaining their own streaming platform. That's time the person could have spent continuing to refine their actual product: travel videos.
Video editing and production are extremely time intensive tasks that require a lot of skill; people work on these skills their whole lives. Likewise, dev ops and infrastructure management are incredibly deep rabbit holes to jump down. The idea that every hobbyist blogger, photographer, and indie band should learn about server administration seems crazy to me.
Does not owning your platform have risks? Of course. Everything has risks and business is always about tradeoffs. Platforms like YouTube solve a lot of problems for content creators. For most creators, those benefits are going to outweigh the costs.
Also, The only people who could do this are already making tons of money. We're talking about people with high technical skills, not the people posting ASMR videos.
You also need to attract viewers to your platform, which is no small feat.
Of course, this gets at another reason why owning your own platform doesn’t make sense, which is that web infrastructure is a specialty that most people have no interest in, and if they did, probably limited innate ability and training.
If it were that easy for people to suddenly pivot into a 6 figure salary field...more people would.
I suspect such an industry does exist, but it's quite a bit smaller than both the number of people profitably creating content on YouTube and the number of employees of YouTube itself, which tells me that maybe the risk-adjusted returns of it aren't as great as you think.