Because it's all keyboard based. Depending on your field of work a good UI can be very different.

A few years ago I watched an account work through my companies numbers using their accounting software. It's entry method? A windows commander like tool. The menu options like add expense etc were all numbered. So he never left the numeric part of his keyboard.

The tool looked super old and obsolete but as soon as you see a power user use it, you see why.