I'll give the deep spiritual reasons and then the superficial reasons:
1. I have a deep desire to please others and feel useful or important. Sometimes as a man, you need that validation from other men. Sucking cock is one way that I feel this.
2. It's the one sexual act that truly brings me into the present moment. I feel at peace like a meditative state where the only thing that matters is this man's penis. The beauty of men and masculine energy is that you can let them be dominant and you get to be submissive, which takes you out of your own mind and grounds you into the present. No overthinking, no decision making, let him do all of that and lead you. Your only purpose is to worship his penis and do whatever it takes to get him to cum.
3. Making a man cum feels like a true accomplishment. I practice acceptance, surrender, bravery, and dedication by letting his penis and his desires overpower me. Swallowing his cum is what makes me feel these things the most.
Now the superficial reasons:
I honestly just love how a big hard penis looks with a ballsack hanging there. It's so masculine, so completely not-feminine. I love the helmet shape of the glans and I can't control the desire to want to put it in my mouth and feel it with my tongue. A penis has so much presence, weight, and strength and I love being near the energy that it radiates. I love the smell of a man's crotch, all that muskiness; it's pungent and intense, far from pleasant like a woman, but very intoxicating. And the way a man's flesh tastes, sucking on his balls, licking the sides of his sack where the top of his legs are, it makes me feel so perverted and dirty that I like it. Finally, the best part about sucking dick is that men cum...as intense as the experience of sucking a cock is, getting your mouth stretched out, your throat rammed, your face and tongue slapped with a big weighty meat stick, as if it couldn't get even crazier, it all climaxes with a man putting you through a true test of your desire, by shooting in your mouth a substantial amount of something that comes out of him that doesn't necessarily taste good and is the weirdest and most unique thing that probably exists on earth. And the expectation is that you will taste this in your mouth and swallow it every time. Sucking dick is not for the faint of heart, a man's pleasure really requires a lot of you and personally, I love that it requires so much.