No one truely knows why, but this is the best explaination generations upon generations of betta keepers have come up with and joke about~
once you own bettas, you are bit by a parasite they carry, we call it the betta bug... which causes an extreme addiction to betta fish in general. Symptoms include being unable to buy or breed enough bettas, constant thoughts of bettas, uncontrollable ravings about bettas and their care to LFS employees, and being glued to your betta tank. While it is a sickness that you'll never loose, you'll be able to live happily with it, though your wallet may disagree. Note, it is highly contagious, so use caution when interacting with both people and bettas together.