I'd question even that. Hardly any user knows how their phone works, so why would cars be any different? You probably should know basic maintenance but most cars tell you what they need anyway.
I feel like for 10 of those years, it's acceptable. Maybe even like 12-13 because everyone doesn't learn at the same pace. But for at least the last 5 years, this dude was living in a kind of ignorantly blissful haze that makes me envious of his carefree life.
the real "how are you this retarded" is not from op. the real "how are you this retarded" is expecting people to understand how the devices they're using work.
anyone that never had to work on something or troubleshoot problems with it will not have an inherent understanding of how it functions.