I agree with you Dawn ABSOLUTELY!!
I'm sure it comes from the many years of showing dogs and teaching obedience classes. I take my dogs to PetSmart on occasion and it drives me insane when people let their dogs run up on mine.
I have collies, one we had from a pup the other from when she was 2. They have both been socialized and are very good with people and other dogs but the one we didn't have from a pup can be spooked if she is startled.
We were at Pet Smart a few months ago when a dog came at her from behind. He scared the bejebbers out of her and I. She barked at him and sounded very aggressive but thats it, she won't bite or snap. The owner got mad at me. I told him to keep his dog out of my dogs behind and if his dog wanted to approach another dog , he should have the courtesy to ask, not assume. When I taught obedience classes, we couldn't stress this enough to our students.
Some people take their dogs to PetSmart to socialize them, so they may or may not be friendly. We would suggest this to our students all the time.
Pet Smart is not a dog park. IMOP I'm not a big fan of dog parks. But will occasionally take my dogs to the usually controlled environment of a store like PetSmart.
If people are inconsiderate and let their dog come near mine , I just say quickly please keep your dog away, mine are aggressive and will bite. Usually the owner of the other dog can't get away fast enough.

But if you are nice enough to ask, my girls love to play and sniff.