A man who gets himself "snipped" has only a one in five thousand chance of impregnating a woman. I'd call that a bit more than just frustrating any "natural order". Again, my point is that gratification has always been an end to sexual relations and that there's nothing wrong with that. After all, millions of women still crave sex after menopause and we can't be discussing procreation as the primary directive at that point can we?
I'm not saying that self-gratification isn't often -- if not always -- an individual's prime reason for engaging in coitus. Quite frankly, I doubt anyone would even do it if it weren't pleasurable. I am, however, saying that personal orgasmic pleasure is not intrinsic to coitus
per se, which by definition is an act involving one man and one woman. The act of coitus is naturally ordered towards procreation, even when that end is frustrated, either naturally -- such as in menopause -- or artifically.
To put it another way, sex is naturally ordered toward survival of the species, not an individual's pleasure receptors.