I don't think any of us knowingly mean to support pet shops that sell dogs from puppy mills!!
I myself have bought 3 dogs from pet shops, I didn't know anything about where the puppy's came from. I thought everyone bought their pure breed dogs from pet store in the mall and to me that was a luxury. Oh boy what a eye opener it was when I found out the truth
Back then there was no Petco or Petsmart, yes I'm old...lol