OK, I guess the truth lies somewhere in the middle but we're getting off topic here.
I was asking why someone who trains straight punches relapses into haymakers. You can ask why someone who trains hip throws relapses to a double leg but that's a bit more complex, right? So lets focus on punches.
Because they don't train punching that much, they're not boxers, they're MMA fighters. Tthis is why you never see boxers ONLY throw wild haymakers, and even the most slugger/brawler type of boxer will still come in with jabs, and throw straights occasionally. It's really not that hard to comprehend, that a lot of these MMA fighters are grapplers first and foremost, the majority are HS wrestlers, BJJ guys, Judo guys, or guys who joined an MMA gym and have been learning more grappling and kicking from Muay Thai/Grappling coaches, than actual Boxing from boxing coaches (who most likely don't generally work in MMA gym). Or they come from Martial Arts heavily focused on kicking if it's not grappling. They don't train their punches in context to the degree that boxers do. MMA fighters, a lot of them, they only hit pads, and the bag, but when the chips are down, they revert to their most primal instincts, which happens to be the grappling they've been working on, and haymakers out of desperation.
That's why I took up boxing myself, I did Muay Thai/Sanda for years, and though we did hit pads with our hands, and we did punch each other in competition/sparring... kicking is so much more heavily favored and scored in the sport, that it completely over shadows the punching, when you think about it, you don't do much punching, most punches are to set up kicks, at least at low level fights. On the other hand, in boxing all they do is focus on punching, on sparring with punches, it's all punches and only punches. Boxers become more comfortable with punches since it's all they do. So when they're fighting, they'll throw punches the way they've been doing since day one, because it's all they know and practice.
I won't deny that Fight I.Q. if that's what you want to call it, has something to do with it. Some guys can keep calm and keep their composure more than others, and that definitely helps them throw more technical strikes.
