It's truly sad to see these kind of things happen but yet I see it all the time. I work for Petco as many else of you might. We are trained to talk people out of these situations and do everything we can to get them into betta's instead of goldfish in bowls. (Though i really dont like that idea a whole lot either, its a decent out.) Most of the time, I am able to turn people away but every now and then, you get that one customer that just insists (and thinks that they know way more than you) that you sell the fish to them. So I have to sell it, but I am able to revoke the guarantee on the fish so they cannot replace it if it dies. Works out well because a lot of the time the people come back all surprised and say "Well it just died, can I get a replacement?" I just look at them and give them a big told you so and say NO. People will learn eventually after they start losing money. Until that day, there still will be goldfish in bowls, oscars in 20 gallons, and plecos in 10 gallons. Sad, but it happens.
**Just a note, even if you're not an employee and you see these situations, speak up, it helps everyone out