The ich shows up due to the stress of shipping and not from poor conditions at a store most of the time. Shipping is the number one reason for dead fish you see. It is incredibly stressful for them. If they can survive a few days after arrival they stand a better chance of surviving. Putting them in the wrong type of water has no excuse.
I would generally agree with this, but I've seen most "mom and pop" stores where the fish are FINE, and I'm sure their fish are shipped from somewhere too. Could be smaller shops tend to buy from places where the fish are housed better, but still. I'd support a small local establishment before I'd go to a chain store.