Because the screen, keyboard, and especially trackpad on a $200 Chromebook sucks?

Also it'll be truly too slow. You need to at least be able to access a shared document while a video call is going.

The funniest recurring thing when working at Google was new hires getting baited into taking a Chromebook, then not being able to switch to a Mac for like 2 years. Our team made sure new people didn't fall for that.

Also: the enclosure, and the hinges.