Here's the difference: I don't think that being unable to repair your own car engine makes a car less useful. Sure, if your car breaks down in the middle of nowhere, you might be stuck there for a while until you can get it towed, but that doesn't happen too often, and besides, what are the chances you'd be able to repair your car on the side of the road without special equipment or replacement parts?

But the number of things you can do with a computer expands enormously when you know just a little bit of bash scripting, or python, or even Excel!