Bettas can be found in the foo prints of cattle in rice fields in thailand. I dont think that any fish should be kept in a cup, but a betta can be kept in a properly managed "micro-enviroment" They dont use their gills for respiration, they go to the surface and cature air and store it in an organ in their head called a labyrinth. I to dont think that it is the best place to live, but many people would not be as "in to" fish as they are if it werent for that "Siamese Fighting Fish" they got in a cup when they were a yougster.
Fish keeping may not be as popular witht the next generation if they dont have a place to start, my first fish was a oscar in a 27 gallon tnk when I was 10, but not every one is that lucky. you must take the good with the bad. after all how many kids got there first goldfish in a 90g tank? not to many, most were in a bowl.
gotta start somewhere, most kids today would rather have a cell phone than a cichlid, or a gameboy before a gourami. so where does the next flowerhorn child come from? the kid with the betta in a fish bowl. lets just hope he or she gets educated and carries on the hobby
Quinn
BTW my mom has kept a feeder fish alive in a 1.5g bowl for 7 years.