Because if you go that route then you are saddled with a full linux VPS that you must install things on.

For a site that just needs to load some HTML and run scripts, that is overkill. Shared hosting works fine, and requires almost zero actual system administration skills to maintain.

They're relevant for low-load stuff like a forum. I don't want that on my production server, nor do I want to maintain a second server just for it.

> For a few dollars a month you get a full linux VPS

For a few dollars a year you get a shared host.