I breed pets that just also happen to be feeders as well.
I breed food for myself and the extras get sold as pets to cover the cost of food/bedding.
All of my rats have been selectively bred for color, coat, and ears. All of my rats are dumbos. Some are rex and double rex. I am very particular about my rats and their care. Some of the folks who have bought pups from me still contact me for care advice.
Honestly, I think most small scale feeder breeders are some of the best rat keepers around.
I can bet that most of our rats live better lives than some pets out there. We want clean healthy rats because quality rats = quality food. We also intentionally breed for temperament. Biters are culled and not allowed to pass on their genetics since aggression and behavior is heritable. Not to mention that tame friendly feeders are safer feeders for our carnivorous pets.
And what most people don't know is that almost all pet store rats do come from feeder lines (usually from big commercial breeders). The difference is that our rats are socialized, get a quality diet, and are bred for temperament.