When I got my first betta (some friends were moving and there was no where else for their fish to go), he lived in too small of a tank. It was a tank that my friends had got at a pet store that was supposed to be a betta tank. I ended up moving him into a goldfish bowl (bigger, but no where near big enough). None of us knew any better. My friends loved him. When on vacation, they would have me check on him because they were worried about him. We certainly would have never knowingly done anything to hurt him, and everyone involved were experienced pet owners. We just did what we were told. (Listening to what I was told worked with other pets I've owned.)
When I got my second betta, I did some research to buy him a new tank (there was a bit of time between the two bettas, and we gave away all of the first bettas things) and learned that he needed a bigger tank. My second betta has a five gallon tank. In fact, some of the spoiling he gets (and he is a bit on the spoiled side) is out of guilt for not taking as good of care of my first betta.
I got my second betta at Petsmart. I've gotten all my fish at that same location, and they are good. Every time I buy tetras for the big tank, they talk to me about what fish I have to keep the tank from being overcrowded or having incompatible fish. When I bought my betta, they talked to me about my set up and gave me several brochures on betta care.
All this being said, it does make me sad how many fish (and other animals) are poorly cared about because parents think it's cute to get them as presents. This is a living creature! Take care of it! I got my big tank for my eighth birthday. My parents researched everything. They knew I couldn't handle a tank at that age. They took care of those fish. The only thing I did until I was older was feed them, and if I hadn't done that, they would have for me. They got it as a first pet, in part to see if I was up to having a dog, but they knew that if I wasn't up for it or got bored with the fish, they would take good care of them.