I prefer sucking to being sucked.
It could have to do with my masturbation habits. Using a Death Grip / Grip of Doom has probably desensitized my dick to where the softness of a set of lips, a mouth, and a tongue just don't register that well. I'm trying to "correct" this by switching up my hand use with a Fleshjack.
Sucking also plays into my submissiveness and current bottom-orientation, servicing another man and preparing him for topping me.
The cock itself can also be a nice tool and simply worth pleasuring and enjoying all on its own.