It might be beautiful on desktop, but on mobile it's a very limited experience.
Great showcase on how much data your browser is unnecessarily bleeding to every website out there that wants it.
Genuine, non-rhetorical questions: does anyone know why the hell your browser needs to tell the site
where your pointer is, instead of telling it which elements you clicked and calling a day?
if the window is active/inactive?
the relative position of the window in your screen, instead of just its approximate size?
Hover effects, you often want to respond to the user hoving their mouse somewhere, for instance showing a tooltip.
Battery/network saving, a site can pause animations or reduce update requests when the window is inactive.
I cant really think of a good use for this one these days, it was something browsers had in the 90s (not just readonly, websites could move your browser window where they wanted for a while). Maybe its kept for backwards compatibility.
It might be beautiful on desktop, but on mobile it's a very limited experience.