It's in everyone's psyche to be desired, when you're lacking that, bad things will happen.
This. It's not just about not having sex. It's about being desired, or maybe "wanted" would be another word for it. It has to really screw with you to think that no one out there gets that primal rush or warm and fuzzy feeling when they see you or think about you.
Also, I'm pretty sure this guy made his motive clear, and it had nothing to do with sex