Pet owners are incredibly emotional and protective. If they feel a staff member was insensitive or their pet waited too long, they will vent on Google and Yelp. By placing a 'Tell us how we did' QR code in the exam room, you give them an immediate way to share their feelings.
If an owner is upset, you can address it before they leave the clinic. A simple conversation from the lead Vet can diffuse the situation and prevent a damaging review that could scare off other pet parents.