RE: If you own a pet store, would you let visitors take photos of your pets?
As business owners, they should know not 100% visitors are customers. Yet, many of those non customers can be converted into customers. If people are taking photos, it means they like what they see. If they are also treated nicely by the shop owner, then it is very likely they will eventually buy something. Maybe not today, but the next time they visit.
By making visitors unhappy, it is pushing them toward the door and never to come back as customers. Some people just don't have the basic logic of how to run a business while already jumped onto the bandwagon of running a business.