Depends on what you're looking for, as others have stated. Most pet stores are stocked by mass breeding mill type things (as is common for ALL pets in the pet selling industry). You're correct to assume the conditions may be as bad as a puppy mill bc they are being multiplied to produce a profit- not to continue good genes or much else of anything.
I think the distance maintained in the fact that bettas are fish
while puppies and kittens are more of a personal, cuddly family member
is the line drawn. Most people know a fish has less capacity for feeling than does a puppy who was churned out of a flea ridden, poop matted terrier in a cage. Animal rights laws are different in NA than they are in South Asia (where a lot of the betta mills are), you can find vidoes on YT of Singapore breeders feeding their stock.. They house thousands of bettas before sale, so you can imagine the actual care involved.
I will however point out that some of the mills try new tactics for cleaning and distribution and many workers there are in it for the love of the fish and what they create.
I hate to buy from pet stores bc I don't like supporting stores that sell live animals but I know I provide Lakitu with the best home he could ever have wanted! He came from a tiny bowl and now has a good retirement :)
[ridiculous post over]