I think a lot of it is what you're used to growing up and how much day to day exposure you get to them.
I grew up with computers, work with PCs and play with Macs and I'm reasonably competent with them.
I'm happy to tinker and fiddle with them both in terms of the real physical bits and pieces and what's running on them.
On the other hand all I know about my car is that it has three peddles, "stop", "go" and "push when you change gear or the engine will jump ten feet up into the air".
I'm very reluctant to do anything more major to my car other than wash it in case I break it.
I'm sure if I put the time into it I'd be able to pick it all up, but right now and from here it's all just a great land of mystery that's best left to mechanics who see me coming, circle me like sharks sniffing blood in the water, inhale through their teeth and then can charge me pretty much whatever they like
So it's not mental blocks or old age, just experience and practice.