Yes, breeders and non-breeders. They do it just to get ride of them so they no longer have to take care of them. Gee I wonder why some of them have issues, they need the time to learn how to be a dog and learn independance.
I was an ACO at one time and saw some tiny ones come in to be put up for adption and was told they had no idea who the mom was. They "FOUND" them, yeah right!