I think some have no interest in mechanical issues, other have no aptitude, and others no experience or mentors. My brother and I grew up in the same environment, with our father who built and repaired almost everything himself, building houses and fixing cars and snowmachines, woodworking, welding, etc. I learned from him and the ethos of self-reliance and curiosity was imprinted. My brother, through lack of desire or aptitude, did not pick up the same traits. However he has natural abilities and inclinations I could never achieve, primarily in music and art.
Others like some of my close friends have the desire to build, fix, or just generally wield tool-shaped objects, but never had mentors like I had and just lack experience, but they are on their way now. Anyway you cut it, no man is an island and I generally find no fault in people who follow their own proclivities which require no use of tools. What does grind my gears however are people who use tools to rip-off the mechanically UN-inclined, whether through run of the mill price gouging, deceit, or even worse, shear hackery.