Or: the market does not (always) work. This too is an option.
But, it's still something worth probing into: if it really does make the user experience worse -- and I agree it does -- why haven't people punished those sites by going elsewhere?
My best guess is that it's like bad customer service: it bugs people, but it's not really the differentiating factor when choosing a product/service provider.
I've met many young people who still default to pen-and-paper for things like note-taking. It's tempting to dismiss them as luddites, but I can't exactly blame them, given how much I know about just how user-hostile modern computer software and hardware can be.