Why are there keyboards and pointers? Why not just an input device?

[Michal Suchanek]

Hello,

maybe this is a stupid question but why do we have keyboard and mice
attached as different kinds of devices?

Since mouse events can be mapped even to plain keyboards and many mice
have keys or buttons that would like to pretend to be keys what is the
benefit?

The obvious drawback is it crashes the X server a lot.

Thanks

Michal