Have you ever encountered people who are extremely distrustful, almost angry sometimes, because you understand computers, and understand what they can do, and they don't?

I have. I mostly encounter it in people my age and older, but I’ve come across it in younger folks too. However, the younger folks are more likely to say “Wow! Cool! How’d you do that?” whereas the older just glare and walk away.
What I don’t understand is, why in the world so they get so upset about it?