The mechanics working on the used car lot either are not competent enough to evaluation and diagnose basic wear problems or just aren't motivated to fix what they find.
I recently went shopping at Andrews Automotive hoping to drive off in my new car. Our first problem was that the salesman told us we could not take the car to a mechanic for a pre-purchase inspection. In any situation, if a car salesperson tells you an independent mechanic can't look at the vehicle before purchasing, that person is probably hiding something. Anyway, the salesman conceded that we could take the car to our mechanic if he came along. He went to get the car, but the battery was dead.
The car drove nicely, although there was a slight growl. When the mechanic had it on the lift, we could see some problems with the rear bushings and front bearings. They needed to be replaced, but were not damaging the car. The transmission fluid was also brown, which is another one of those "always a problem" things. The mechanic told us that it was a good car, and that it would be fine once the repairs had been done. Altogether, repairs would have totaled about $1,500.
We offered the asking price of the vehicle less that $1,500. The salesperson said no, but that their in-house mechanics could do the repairs. We also offered to pay full price and have the dealership pay the mechanic directly. No, all repairs had to be done at the dealership.
The dealer had this car in need of $1,500 worth of necessary repairs on the lot available for sale. The people who put that car up for sale would have, without hesitation or remorse, sold a vehicle that was broken.
Had their mechanics not noticed what was apparent even to me in my limited knowledge? Did they just not care? Either way, I walked away from a car that I really wanted.