My old girls do not need a whole lot. My youngsters take more time. But, having multiples is easier in some ways. And, yes, if you breed and are not willing to dump your retired breeding bitches, you will have more dogs than most people can fathom managing.
I can only say, that many of us who breed, who have what others would say are too many dogs, do not have the problems that people with 1-2 dogs often have.
Our dogs are not spazzing when taken to the vet. They can have one outing in 6 or 8 months, and meet people, children, babies, groomers, vets, whatever, and even 4 dogs running at them without losing their minds. They trust us completely, they are happy -- even not living in the house, and eating our left overs, sleeping on our bed; even if they are not worked regularly, tired out before we leave for work; even if they are not socialized as puppies beyond a couple trips to the vet for shots and maybe a trip or two to the groomers.
The dogs are critters, and living outside is natural for them. They can come in on occasion and they like that too, but they are happy outside. They are also living next to, and in many cases in the same kennels with another dog or two, and they generally do not have the problems of separation anxiety, nuisance barking, because they are lonely and bored.
Even if the bitches must be separated, being kenneled next to others in the pack is not the same as being completely alone for hours on end.
I have too many dogs, because I am not actively working toward some goal with every one of them. But, they are all loved and cared for, they all display a level of obedience and expectation for behavior.
I think that it really depends on the dogs. If you have dogs that require work/exercise to be sane and manageable, than fewer dogs would be a must. If you have dogs that want to be only-dogs, then, it can feel over-whelming to have multiples. 2-3 dogs might be overwhelming, where 5-6 dogs are manageable depending on the personalities alone.
Breeders have to be able to separate dogs. They need to separate dogs during heat cycles, and they may need to keep bitches separate altogether, and they will need to have a separate place for dams with litters. Most people who aren't breeders want dogs that get along with each other, and having dogs that will scrap with each other tends to be over-whelming.