Many popular games are physically and mentally demanding. You do need "vigorous, professional mousing" for any kind of shooter or RTS, on top of actual thinking and reacting.

Playing in teams requires you to type to coordinate with teammates. The language floats from cryptic to hectic: all sorts of acronyms, jargon, combining text with "body language", etc. Regardless, typing with both hands is still faster.

You can also buy a detachable numpad.