Good for them! That is as daft as the supermarkets putting sweets and chokky stuff next to the check-out, so if you have a small human in your trolley, they can just reach over and grab whilst you are stuck in the queue!
Perhaps your Pet Shop should have tethering rings outside if they need to display all their goodies at pretty much floor level ... I know a lot of the smaller pet shops are really strapped for space, and maybe they don't imagine people are going to shop with their dogs .... I love those places much more than the sort of hypermart things - they are like Aladdin's Cave to us, so imagine the total sensory overload that must happen when your dog goes into one (like visiting Willy Wonka's Chocolate Factory !!!).