I mean, yes, that is a feature of css, but the idea that web pages are somehow obligated to use that feature or be ridiculed is silly. It’s all about how much the presenter wants to cater to the preferences of their audience. And sometimes, the answer is “not at all. the information is presented in a reasonable way and effort spent on formatting options is wasted.” This is why books are not usually offered in large print versions unless there is a compelling reason like a large portion of the target audience needing it.
I don't think they're obligated, I just don't think the software is very good.
Which is fine. Most software is shit, so they should feel right at home. I'm just not going to pretend that the current state of web applications is at all acceptable.