Reasons Puppy Mills need to be banned from the US:

1. terrible feeding/boarding conditions : they are literally piled on top of each other
2. diseases, illnesses, and depression
3. no human companionship, toys or comfort, and little hope of ever becoming part of a family
4. dogs that aren't adopted/rescued are euthanized
5. after their fertility wanes, breeding animals are often killed, abandoned or sold cheaply to another mill to try and get "one more litter" out of the dog

...result of all this breeding is millions of puppies, many with behavior and/or health problems.