I assume you mean to ask "Why do you like big bottoms so much?" Assuming that's the case, the complete answer would be really long and go into my personal life, so I'm just going to give you the short version. Essentially, I grew up liking guys with big muscles and a good amount of chub. I don't like having to do what others tell me to do, so topping guys I find attractive is really cathartic to me. And there's just more to hold onto with big guys.