I can't recall why. I guess all the women in the game are too screwed up. It's either a witch, some political witch, an evil controlling medic, ho's, some weird green woman that wants to have him run errands, or who knows what else.

That's going to be tough considering witchers are infetile non-humans with an insatiable sex drive.

Um, I've read The Last Wish. Witchers are infertile and immune to disease, but nowhere does it mention them having some kind of libido on steroids. Even if that is a thing in the rest of the books, which I sincerely doubt, barring the game mechanic requiring the player to sleep with someone to keep Geralt from dying, I really don't think that RPing Geralt as celibate should pose any kind of problem in game.

I'm just saying it's odd. Like playing as Charlie Sheen and wanting him to be off drugs and sex.

Simple: imagine Geralt is using a wooden prosthetic (common in that time as it's a bit too early for plastics) to complete the quest. Quest complete: Geralt remains as celibate as a goat on holiday.

In all seriousness, all the cartoon sex in the game is imaginary, anyway, so just insert (oops!) a wooden prosthetic in there and everything is tied off neatly. What happened is actually that Geralt lost his in the war, you know, so he got the wooden job hand made by a skilled craftsman and then had a mage cast a "lifelike" spell over it--and he's in great demand with the ladies but still as virginal as a lamb. It's all in the script, don't'cha know...;)

Except you are operating under the premise that Witchers, and by extension Geralt, have a default mode of being lecherous sex fiends, when they aren't depicted that way at all in the series. Hell, the game actively points out early on that the whole image of Witchers being sex-obsessed knobs that walk as men was actually propaganda spread by people who hated the Witchers in order to get people to storm the castle and try to kill them all, which managed to kill off all but a handful of them.