People are genuinely ignorant about the care fish need. It's the same thing that happens with all small pets, they're almost disposable. Nobody tells you that they may be cheap to buy but they have needs you can't meet if you're an indifferent owner.

The pet store wouldn't get money from impulse buyers if they told you the care you need for an aquarium (don't you have to start a few weeks before you bring the fish to get the good bacteria?) or how actually big hamster cages are. Or that birds are such sensitive creatures.