I'm a keeper. I keep a total of <think quick> 49 snakes and I'm not breeding, although I'm tempted to perhaps do that someday (put a big question mark behind that!). I agree with those here that already made the comment that most breeders are in fact hobbyists that breed purely for the joy of putting a new life into this world. Sounds theatrical, but that would be the only logical reason, since it can't be the money ...
By the time you pay x-amount of dollar for a pair of quality moprhs to breed in order to produce a morph that brings the big bucks, you've spent money on rats and oodles of time cleaning and caring for the pair and the price for the big-buck-morph (in case the snake gods smile upon you and you are lucky enough to produce one!) will have already come down, because someone else is producing the morph already and sells at bottom price.