It's simply not true at all that everyone who owned a (i'll be generous and assume you're talking about PCs) computer serviced their own computer upgrades and part swaps. In the 80s and 90s most people would take the whole PC to the store and get a whole new PC. The consumer market has always been dominated by pre-builts.
About as neat a trick as opening a slot machine, pulling out the mech and fixing a jam.
There is a massive qualitative difference between API knowledge and foundational knowledge. The former is tied to the usefulness of the platform, the person with a macbook or an iphone looks at you the same way you look at a person fixing their car or slot machine. I for one am sick of the gross fetishization nerds do of cheap knowledge.
The same thing that makes your knowledge useful (usable) is the same thing that makes it useless (negative utility). You can only change your likely PC parts because it's long been standardized and a whole industry has ossified around those standards. You've confused learning about computers with learning about a standard. Someone else would roll their eyes at your statement, "well duh of course you can't take an IBM 360/40 to the shop"
