Aside from the obvious lack of breeder's regard for genetic and physical health etc, I think people also underestimate the damage done to very young and impressionable puppies living in those boxes with little to no stimulation, education of socialising, usually for the most formative weeks of their entire lives (from 6 to 12 weeks).
If you took on a foster child (human) who had been similarly isolated you would logically expect a whole word of emotional, mental and even physical issues.
But all too often folks buy their expensive bundle of joy from a pet shop, take it home and expect a model canine citizen. And when they don't and can't get it the whole thing becoems a great disappointment, there's no support available from the store, and the pup ends up being given away or dumped...
Isn't there a new member here who has just taken on a slightly out of control 10 month old pup? I wonder if that one was originally a cute, fluffy impulse purchase?