We've evolved to o-key rollover

Sort of, it's more anti ghosting, or configuring the keyboards circuit in a way so all of the "gamer keys" don't interfere with each other. Ghosting is when a certain combination of keys are pressed tricks the matrix, activating another key that isnt pressed at all, hence "ghosting".

Membrane keyboards generally only have 2 key rollover (sometimes if 2 specific keys are pressed, none else will register). Some gaming keyboards will rearrange the circuit so that these specific combinations aren't present near WASD. For example on most keyboards, if you press W,A,S, the S key would not register.

Most of the time I just ignore it. I game a lot, and have a big expensive PC and high refresh monitor but I still game on a model M. Membrane keyboard with 2 key rollover, but it's never really affected me honestly.