Well, Walmart and Petco are not the epitome of good fish care, to start with. If you go to a very good, locally owned and operated fish specialty store, you will often find the male Bettas will be in full-sized tanks with appropriate community fish. Other places keep them in cups because a) they don't know any better, or b) it's just easier that way. So many people believe the myth that Bettas cannot be kept with any other fish, and keeping them in little cups saves space.
All fish need filters, and Bettas need heat, they are tropical. Little bowls don't allow for heaters and filters, and don't give the fish any room to swim. And swim they will, if they are properly kept!
How long have you seen someone "successfully" keep a Comet Goldfish in a bowl? Surely not long, as these fish can reach 18" long at maturity! They should live 20+ years, when properly cared for. They are waste factories, and will soon die of their own waste, if the tank isn't maintained constantly. Without filtration, and constant cleaning, they won't live very long.
I am surprised that you can keep a ACF with Guppies. Mine is in a tank by himself, cause he tried to eat my Cories. They will eat anything they can stuff in their mouths. An African Dwarf Frog is a different story, though. They are very peaceful.
Keeping fish in tanks is cruel if the tanks are too small, or not properly kept. However, well kept fish are not being mistreated in the slightest. They don't have to hunt for food, are not poisoned by pollution, and don't have to hide or run from predators, as they do in their "natural habitat." Wild caught fish sold as pets are a problem, and are having detrimental effects to ocean reefs. However, fish bred in captivity, if anything, contribute to non-extinction.
The debate over whether it is humane to eat fish (or meat) or not has been going on forever. Everybody has to decide what is right for them. I don't eat fish, because I just don't like it. I don't criticize those who do, however.
This is my opinion, and what I know. Hope it helps.
Hobbyist for many years.