Why do some guys have "wet dreams" multiple times a week, yet some guys don't have them at all?

Where does the semen go?

Many guys who masturbate regularly never experience nocturnal emissions. For guys who rarely or never masturbate, if the semen isn't ejaculated in a nocturnal emission, it may be simply re-absorbed by the body. It's largely a matter of genetics whether the body is more likely to deal with the matter through a "wet dream" or not.