This pig gets off on many aspects of the act of cocksucking. For one thing it really loves being used. Even though it loves the sensation of a cock in it's mouth, that is secondary to providing service to strangers. Like others, it loves feeling a cock harden up in it's mouth. It also loves how a cock feels laying across it's face as it sucks the man's ballsack. Another thing it likes is the humiliation of a man jacking off over it's eyes as it sucks his smooth ballsack. It really likes a verbal top and a hand on the back of it's head. It also LOVES the gloryhole and for the men to be noisy and verbally abusive to the pig so other potential cum donors know why it is there. It loves to beg for cum. When it gets some, it always tells him how good it tastes and how grateful it is for the gift of his semen. Even though it likes the top to encourage it during the act, it never wants to be thanked after. In fact, it wants the man to barely acknowledge it once he ejaculates on it's face or in it's mouth.
It all boils down to the fact that it sucks cock because it loves to be USED. While it absolutely loves every sensation that accompanies a cock or ballsack in it's mouth, it does it for the top and his pleasure, and for the feeling of being treated as an object rather than a person.