You can still cache things locally, it's just shouldn't be something the user has to be aware of. What I'm typing now isn't immediately being communicated to the central server every keystroke, there still is local state, but it's still a client-server architecture.

The repos I work on are often smaller than the average webpage, I'm really not buying the idea that in the age of HD streaming bandwidth-concerns are an issue here.

Incidentally none of the teams I've worked on ever even use any git features like bisect. The cult of git means everyone has to use git, even though for most people that just means many hours wasted googling with absolutely nothing to show for it (as in git is strictly inferior than just sharing files across a networked drive for many teams' use-cases).