off the top of my head, he's been wearing a BDSM cup that's crushed his penis and balls against his body. Combine that with hormone drugs and gel, poor diet, and general laziness. Before that, his duck was notoriously bent, looking like a big toe that had caught on a door frame. Seriously, in all my research as a prawnhub PHD professor I have never seen a willy with a knuckle. Then throw in a knife wound and piercing to the gooch, wearing panties which are not ergonomically designed for dudes, and we're left with a eunuch.
Sometimes I wonder if Christian's low effort pursuit of the love quest was down to experiencing sex as a male, and then finding it extremely exhausting. For ladies, the option of impersonating a starfish and lying there is open, but to men, you're expected to at least put a shift in, if you're expecting a repeat performance. Allegedly one, or two collisions with a prostitute, and he gave up. Assuming these events happened, he put his libido aside, and treated it as an accomplished task. Maybe he found the sex painful, uncomfortable, or barren when with a woman only using her sex in a mercenary fashion. Or maybe he did the math and thought prostitute money garnered less pleasure than transformers and pokemon money. Rather than find something new, exciting, and stimulating, he abandoned the quest, aside from trying to become a prostitute himself, and get women to pay him for his 'tribbing'
I've heard it theorized that Chris might find it painful, because during the smash mouth video he's grunting or crying. By that point he'd done irreparable harm to his gnarled growth. Maybe this is why he tries to focus on scissoring. Or maybe, just maybe, a part of him realized the only thing that plans on fucking him... is life.