Yeah that's true, finding out why they're selling it is a good idea, I got an 04 dx from a guy who was moving out of the country and it was in great shape (he wouldn't have sold it if he didn't absolutely have to and you could tell he loved it haha, I kind of felt bad for him but his loss was my gain), also he just seemed like an all around good guy, he even threw in a camp stove and some fishing poles that the mover forgot to grab (also he happily let us test drive it and kept detailed records of all the major -and minor- maintenance he did on it, and was the original owner so he got all his oil changes brakes and tire rotations done for free regularly at the dealership, definitely a plus). I think the best cars would probably be from a case like this, moving and can't bring the car, or a car owned by someone who passed away that's being sold by a relative who has a much better car and lots of money and has no use for it (although those always seem to sell the fastest so they'd be harder to get, idk how many times I found a craigslist ad for a car like that with low mileage good carfax and a great price that were already sold within 30 minutes of posting - of course due to this I never actually got to check any of them out so maybe they weren't quite as incredible as they appeared from the specs)
Depending on how much money the person selling it has I feel like a car that's being sold because they got a new one could be good or bad, if they're rich then I could see them just buying a new car cause they wanted one when there's nothing wrong with the one they're selling, but if they don't have money to throw around like that (this applies to most everyone I know anyway, although I'm sure there's plenty of exceptions) I couldn't see them getting rid of a car until it's become too much of a money pit to hang on to or too much of a pain in the ass to work on themselves
Another tip that was pointed out to me when I was car searching was to be wary if the engine and really everything under the hood looks way too clean and nice for the price and age of the vehicle, I guess it's more of a dealership practice from what I gathered but they'll clean everything up to make it look nice so that people assume it's in great condition and don't check into it much further (of course it could also mean that they just keep everything in really good shape but it's worth a deeper inspection anyway)
At this point this thread is kinda old so I'm guessing you've probably already found a car but I figured I'd chime in since it's the internet and I can pretend like I know stuff
(also I'm always getting information from here and never giving any and this is probably the only topic that I actually have firsthand experience with haha)
Hope you found (/find) a good one! <3