I mean, I've seen people have some dumb principles, but not using a controller because of principles would be up there to take the cake together with some of the recent ones I saw around Dragon Dogma 2.
I personally only use a controller if the game is a console exclusive. When I play on the computer I multitask a lot and it's just too much overhead to put one peripheral aside to use another, it requires more space, and to me, also a different distance from the monitor I'm not comfortable with (I need to back off a little so that when I hold my hands with the controller the desk doesn't get in the way).
All things combined are mostly the reason for I'll use K+M in every PC game, even when it's suboptimal, just because it's more comfortable and convenient to me.