It might not have crossed you mind but used car parts do not come boxed and barcoded, they need to be stripped from existing cars to a safe standard standard as well as comlying to strick rules on not only how to dispose of the vehicle but the fluids and fuel withn. Getting the right cars in to match the needs of buyers can also be complicated. There is an abundance of cars taken off the roads each year, but finding the vehicles where there is a demand for the used car parts on the car is not easy, so brekers yards end up scapping mosts of vehicles that do come into the yard becuase they are the wrong make and model.
Here is how they do it in the USA.