Why do men watch porn?

I am not stating all men watch porn, I'm just genuinely curious as to why some men in relationships watch porn? Same goes for the woman in said relationship. I'm trying to be "ok" with porn but can't get over as to why my SO wants to watch it. (We only watch it together) he tells me he gets more turned on because I get turned on. But is there actually more to it? So that's why I am asking this question, why does your SO? What turns him on from it? What turns you on from it as well? Definitely the MAIN question here is.. what turns said person on while watching porn? Is it because they find the person attractive? Or what?