I think the most frustrating aspect of used car shopping is that so few people keep any kind of maintenance records. I'm incredibly OCD in the department and keep receipts/invoices for anything related to the car and log every time a fluid is topped off, wipers replaced, as well as every fill up.
It's mind boggling that so many people keep zero records and then expect to sell their cars for a premium price. I've looked at so many cars where the owner couldn't give me an answer as to when the ATF fluid was last changed or if it still had the original timing belt. I don't look down on people who don't know much about cars but if that's the case, they absolutely should contract that service out to a good mechanic and keep records. My grandmother knows absolutely nothing about cars or car maintenance but she's gone to the same mechanic since about 1970 and has had the most meticulously cared for and well documented cars I've ever seen.
Years ago, I was told that part of the reason the used car market seems so inflated is that 100,000 miles was the magical cut off point for auto loans. Therefor, any car with < 100,000 miles kept an inflated value and then plummeted when it 100,001 miles.