With all that in mind, why is the seemingly innocent bar of soap the weapon of choice for these lusty prisoners? Well, if you think about it, what would you normally do when you drop a bar of soap? Easy! You'll immediately pick it up, right? Well, picking it up would leave yourself open to sexual predators who are just waiting for a chance to pounce on someone else's ass. They just have to look the other way as they plow that poor guy's ass deep and hard, thinking that it's actually a woman's vagina instead. And that means they're already desperate enough to settle for another guy's ass instead. Even if some of them are straight, the fact that they haven't had the chance to touch a woman's body in like forever, they would rather settle for anything that resembles a clean, shaved vagina.
With dozens of other guys taking a bath in the same room, at the same time as you, there's no saying what's on the minds of those sex-depraved convicts. In prison, it's already common knowledge not to let yourself be a victim of picking up soap in the bathroom.