i always thought it was people of a certain age who required inversion (i include myself here) because the first 3d games were flight sims, so pulling back on stick/down goes up etc.
At least for me, I've always associated preferring mouse inversion with growing up handling BB guns. When you're lifting a rifle up, you are pulling back/contracting on the right arm. When aiming, to go up you nudge the right hand down, or nudge up to point down.