Honestly copper treatment willy-nilly at the lfs is not always the best option. Copper is a toxin and fish should not be exposed unless necessary. Also, a fish brought in to the lfs today and placed in copper tank will not get full exposure to therapeutic treatment unless the lfs treats that fish for a full 3 weeks AND is maintaining appropriate levels of copper via daily testing. I doubt you will find many stores doing that, if at all. The goal at the lfs is to suppress ich long enough to get a sales and the fish (merchandise) out the door. It sounds Machiavellian, and many stores won't see it that way, but essentially that is what they do. More power to any store that takes actual QT measures pre-sale. It's not cost-effective for them, though, and the customer base encourages this by looking for the best bargain rather then the best, well-cared for fish. If people buy a furry pet, the approach to acquisition is usually quite different.
The hobbyist can't take shortcuts with disease prevention. It is on us to take measures against introducing diseases into our display tanks.