I often wonder if browser vendors, or anybody really, believes that this sort of thing makes our world better.

All it does is add a third case that every application needs to support from here on out. You need to do your sniffing, then register mouse events or touch events or pointer events as necessary. And write similar but different code paths for each case. And you need to maintain and test all three of those branches for ever.

It's that XKCD comic. And that Joel blog post from fifteen years ago. Implemented with no irony whatsoever by people who seem not to have read either.