but I've always thought it was strange that people will spend days learning about, debugging, and fixing their car or computer...
Who are these "people"? Sure, there are some who will do this - and this being Slashdot, we've probably got a population enriched in them - but if you take a random person with a car or computer problem, they will just ask (respectively) their local mechanic or teenager--in exactly the same way that many people approach their doctors.
Yes, there exist people who will try to troubleshoot their cars, computers, or their own bodies. And there exist subsets within those groups who can are capable of doing so in a way that makes things better rather than worse. Most people aren't comfortable going beyond the most basic diagnostic steps in any of those three spheres, however. Putting gas in the car is their limit; checking the oil and topping up the washer fluid is something that happens at the dealership, and borrowing an OBD-II reader to interpret a Check Engine light is in the realm of black magic.
Worse, there are also people who spend good money on magic grounding straps for their cars, insist on clicking on VIRUS WARNING links in spam emails, and who actually believe stuff that homeopathic practitioners tell them.