Most breeders that supply to petco/walmart/petsupermarket/petsmart aren't breeding to supply the stores. They sell the fish to the stores to support their more complex and special breeding. They're trying to be the first to produce much better bigger more awesome betta.
Petco has started handling halfmoon, double tail, delta and king. This is great because it encourages interest in betta but its also bad because the standard practice is to have a selection of every type on the shelf instead of limiting the total number better. But even this situation doesn't stress me too much.
What distresses me is when I go in to a petco or a walmart and someone cupped a girl who is still a fry. Fry run on little fish hormones to grow, their water conditions never have a chance to go bad because the fry can't eat the food the store gives them IF they feed and they're not big enough to soil the water from what they've already eaten.
Friday I went to see about a couple girls and one of the three small ones woke up to say Hi to me then I watched as she exhausted what little energy she had left responding to my attention then fell over on her side in the bottom of the cup. She woke and tried to get air but died within thirty seconds, little fish bapping her eye against the bottom trying to make her body work. If you want to be incensed over treatment, be angry at the breeders and suppliers who cup fish that have zero chance of survival without immediate purchase. There's a difference between just getting too many and hoping people will buy them so you don't have to cull them and shoving it all out the door to reduce overhead.
I brought the manager back there and described to her what happened loudly enough for all the parents to hear, she'll remember to discuss it forcefully with the supplier. I left with two girls, Fins and a red one I've not named.