The bad breeders force the dogs to get pregnant for more baby dogs. It is very bad for the dogs health and it may cause infectious diseases for baby dogs. It's a breeders selfish decision for making the dog pregnant, as they are just thinking about the profit they make.
The breeders often force inbreeding(breeding with relatives or within a family) which leads to mental health problems or diseases for babies. If people stop buying dogs from pet shops, those awful breeders and pet shops number will eventually decrease, leading to more dogs and cats being saved. Some people believe that it is better to get a dog from a pet shop but it is actually better to get them from a shelter or a good breeder. I think it is important to change people's impression about shelters and breeders to think about where they get a new dog from.