Why can’t someone in their 70s know about computers? I had an email address before you (or even Joseph, according to what he admits) was born. I used the internet before there was such a thing as the world wide web. I had a personal computer within a few years of the first one ever. I ran extensive programs on a computer the size of a building (from a mainframe terminal, ever heard of one?). I daresay I know a lot more about computers, programming, networks, and hardware than many or most people younger than me.
Your stereotype may be correct in general, but you can’t apply it on an individual level.