Though they are not ideal for people who want bettas as pets, those small tanks do come in handy for other reasons.. such as hospital tanks and tanks to keep breeders in, or juveniles when separating from a spawn. I use 32oz cups, and my tanks holding my breeders in (except for ones I am growing out) are all under a gallon. Also placing a couple females in 1/4g containers to stop their growth. I don't suggest them for pets though, as a lot of people don't want to have to do the frequent water changes needed in them. And normally don't have the set up/way to properly heat them. But having a small tank of a gallon or under can come in handy when a sick fish needs treatment/isolation.