A breeder that will sell their dogs without papers is often a back yard breeder or commercial breeder who does not do any genetic testing and for a lower cost you could end up with a puppy that has luxating patella's, leg perthies disease, cataracts or perhaps something worse like a liver shunt or heart defect. To fix these things could be very costly. Overbreeding, poor breeding, breeding dogs that should not be bred and breeding without genetic testing produces masses of puppies which can then be sold cheaper. But then, such breeders are producing quantity not quality. The fall out is that unsuspecting families are left with a poorly bred dog that may have an assortment of health and other problems down the line. What is saved initially is often paid out later in Vet bills and heartache.
"Without papers" is a term used in regards to unregistered dogs
"With papers" is an every day term for a registration certificate