In the old days of scan codes the left hand side of the keyboard had (in general) shorter keycodes than the right hand side, so could accomodate more keys being

In the old days of scan codes the left hand side of the keyboard had (in general) shorter keycodes than the right hand side, so could accomodate more keys being pressed. People started playing fps with the big keypad, but you'd often run into issues where you could only use 2 or 3 keys at a time. Several games such as Duke Nukem etc came with utilities in which you could check if your specific keys would lock the keyboard; after that the default movement keys switched to wasd. For myself I preferred to use 1 finger per key, so I switched to escf.