Everyone played Quake with arrow keys at first because its controls were still archaic and mimicked Doom. Mouselook had to be enabled with the +mlook console command, and otherwise holding / would allow you to “mouse look” but only up and down, and only as long as you held it, and it would spring back when you let go and moved. Thus nobody was likely to figure out mouse aiming by accident just by messing with the mouse, or even by exploring the available in-game options.

Quake’s controls did not define the standard FPS layout going forward, rather the modifications people made to their setups for deathmatch did.