My father is 85 and is quite good with computers; he uses email constantly, writes documents and books using word processors and understands the concept of files, reads on a Kindle, etc. But he had never touched a computer before he was maybe 70 (let alone own one), and before that he wasn't technical at all. He was trained as a Latin teacher (!) and spent his professional life in politics, never having to type anything by himself.
My father-in-law is very good at many manual tasks including woodworking, electricity, electronics, and was an officer in the French army for many years, where he was responsible for maintaining highly technical weapons. He too is 85 and he can't seem to understand computers, although I have known him for 15 years and have been trying to help him for that long. He seems to want to learn but isn't really interested in what one would call "the big picture", he just wants to know a list of actions that will get them to where he wants to go. Of course that approach fails miserably whenever something happens that's not on the list.
I have two friends who have been to top engineering schools who, I discovered recently, type whole urls not in the browsers' bar but in Google's search form. My eldest son is 11 and doesn't confuse the two. My younger son is 7 and doesn't seem much interested.