I don't think all people who work at fish stores like it much either, many of them being hobbyists themselves. When I went to purchase my gorgeous orange/red Betta, the clerk asked, almost reluctantly, "Do you have one of these cups (pointing to the Betta Bowls)". I said "No, I'm not dooming him to a life like that. He has a home in my nice 20 gal".
She said "Oh, that's so good to hear".
But they don't have any other choice really, they're told to keep them there, or they get canned. All about the $$$. Although I will admit some stores do take good care of their bettas in cups. A store near me called Super Pet has many employees who seem to be quite responsible and compassionate towards fish. They've never given me false information, and their Betta cups are always sparkling clean, with the Bettas looking very healthy and attractive. The whole practice is unfortunate but at least some stores try to make the best of it.
edit - oh and just for the record, there is no debate as far as im concerned. it's simply unacceptable, so it's not up for debate.