I assume it is the same most everywhere, but around here most of the independent used car places deal in the cars that the major dealerships (Ford, Toyota, etc) don't want to fool with. They will take them in on trade on a newer car (for below wholesale) then wholesale them over to the independent dealers.
There's a variety of reasons the big dealers pass on them, maybe they are just too old of a year model. So that doesn't necessarily mean everything wholesaled is a total lemon, but some of them are.