Agreed, but what "prevents" it is that making a good keyboard-driven UI takes a lot of taste, extra effort to build it, and it must be revisited any time the UI changes. It's duplicated work.

Ideally all GUIs/TUIs are usable with keyboard and mouse independently.

A good example of this is when you have a fancy keyboard-driven workflow yet you can't even do the most trivial task without placing two hands on your keyboard. Sometimes I just want to reach over and do it with one hand on the trackpad.

> extra effort to build it

Also extra effort to use it. This is why we have the “how do I exit vim?” meme.

A good user interface needs escape hatches so users can keep their head above water while they learn to swim.

Most of what people want when they say keyboard-driven is closer to a cockpit (requires expert knowledge) than a general purpose UI.