[manicdee]

The more realistic explanation is that the toolbar takes up space and every pixel has value on smaller screens. Moving the toolbar out of the way when the user is not likely to be using tools makes sense when understanding the web from the perspective of someone reading articles.

This behaviour is hostile to developers, not users. A more cynical commenter might suggest that you're the one engaging in user-hostile behaviour with hovering elements and overlays.

[danielvaughn]

(1) the browser is an application platform so devs are users as well, (2) making it harder to develop good UX by not following the spec _does_ make the experience worse for end users, and (3) "hovering elements and overlays" were just a couple of examples - there are tons of reasons why devs need to reliably know where the boundary of the fucking screen is.