Is the use of reproductive organs for things other than bodily functions appropriate?

From what I was taught in school, the is used to not only relieve bladder function, but it is also used as a delivery mechanism for sperm in the reproductive process. To me, injection of sperm in to the or the mouth serves no purpose in that impregnation (i.e. reproduction) can not happen in that manner. If this is the case, then why do s consider these non-reproductive acts to be natural?