I used to work in a tire shop and we had the same practice. It is not because of aftermarket wheel sales. We did not want the liability of recommending equipment that resulted in damage to the vehicle. I am not saying that the spacers always cause damage. The problem is that sometimes they fail. Failure of a part that is holding the wheel to the car is never a good thing.For the record I don't have any either. I do know my local tire shop does not recommend them, as they mess with one of the most important connections in the car: wheel to hub. Granted they also make money selling aftermarket wheels, so a grain of salt is probably worth applying.