In truth, it's quite a lot of work to manage and maintain. Now there are say Docker Wordpress images that can be set up in ten minutes on AWS. However part of self-hosting is that there's no technical support - you're on your own if something breaks, there are updates, etc. Whereas a managed service abstracts all that away, and thus is appealing to a mainstream audience. While we at HN may like the technical side of things, many creators are uninterested in spending hours debugging a performance issue and want to write/draw/etc.
Personally I have servers in my basement and run a Matrix instance, OpenVPN, and a webserver (static site fronted by Cloudflare) as my publicly exposed services. I also have additional services like Landscape and network storage on LAN. When you run all those services, you don't just follow a guide, set it up, and leave it. While that may work for a couple months, something will break eventually and you'll have to scramble to fix it without understanding why. To do things properly and get good uptime you need to understand how things work, why they're configured that way, and have good backup and recovery practices. Security is also another factor, especially if you are storing private or confidential information.
Also for creators, there are services like Youtube and Twitch which are pretty much impossible to replicate without massive cost and infrastructure. If you're just doing text and images, then you could use a VPS or a CDN fronted homeserver and operate your own website. I'm not a vtuber, but if I was it simply wouldn't be possible for me to run my own service even though I'm interested in this stuff.
The only thing I really can recommend is to keep local copies of all your work on disk, properly backed up. Then at least if you lose access to the service, you can bootstrap again somewhere else.