Thank you for your response I appreciate you taking the time to address my concerns. I would just like to comment on a few of the things that were said in your email.
Firstly all fish produce waste and therefore produce ammonia, and in those tiny cups the ammonia builds up very very quickly. After reading your email I decided to get a betta from petsmart and test the water myself. Even though you claim that the water is changed frequently enough, and that the bettas don't produce much ammonia, the test of the water revealed an ammonia level of nearly 4ppm. Any ammonia is problematic for fish, and levels over .25ppm are potentially fatal, the fact that this betta is still alive is amazing.
Bettas do not require filters because of an organ they possess known as a labyrinth organ, which allows them to breathe from the surface. It has nothing to do with the amount of waste and ammonia that they produce. With that theory you could argue that small fish such as neon tetras, who produce less ammonia then bettas do, can live in tanks without filters, which simply isn't true.
As for the water change concern, daily water changes will do much less damage to the fish, and cause him much less stress, then allowing the ammonia levels to build up in the cups will. I change 100% of the water in my 1 gallon tanks every other day, it does not stress the fish out much at all, in fact they love the fresh water they get.
I do not want to come off as rude but, as a someone who has been keeping these fish for over 8 years, I assure you that I know the difference between a crowntail and a betta with fin rot.
Fin rot is a bacterial infection most often caused by poor water quality. Fin rot is easy to spot, the betta will display patches of missing fins, the infected area of the fins will have a black or brown outline, the fins will appear to be rotting off. Fin rot in itself is serious, and can lead to even more serious ailments such as body rot or blood poisoning (septecemia) both of which are potentially fatal. Fin rot is easy to prevent and relatively easy to cure. Clean, warm, ammonia free water is the key.
Here is a crowntail of mine
Here is a veiltail male of mine with fin rot that I got from petsmart
And here is a halfmoon male of mine with finrot that I got from petsmart
Both of those fish are now healthy and beginning to grow their tails back. I do hope that you will read this and really take into consideration all of the information that I am providing you. I would like to believe you when you say that the bettas at your store are well taken care of, but the finrot on the fish, the cloudy water, the dead bettas, and other problems that I witness with my own eyes when I go in your store speak louder then your words.
I hope to hear back from you after you read this, and I thank you for hearing me out.