Would someone explain this to me.....?

I also think that it is largely due to the sales reps in pet stores. Most folks decide to get the child a fish and this is recommended to them by the store as easy to keep, very hardy etc etc and they are given this information from the get go. Not all people are going to hit the internet and research how to care for something they feel they have already been given that information on. And of course, not everyone agrees that they need large spaces. Since there is so much conflicting information, people are just going to do what is best for them and not what may be best for the betta.