I mostly skimmed your other thread where you tried to brainstorm why men prefer the vagina over a hand (theirs or hers). The answer is not as complex as you seem to think it is.
There is an evolutionary reason why the male of the human species prefers vaginal intercourse. It is what continues the species. The human male is biologically wired to prefer that method of copulation over all others because it is the "gateway to life."
To use another example, male felines have a barbed penis. Mating, is thus, incredibly painful for female cats. However, when the female is in estrus, despite the pain, she is receptive to the male. The barbs on the male cat's penis actually stimulate her brain to release eggs when they scrape against the vaginal wall. They also serve to scrape out any competing male sperm because female cats will mate 100s of times with multiple male cats when in heat. The female not only takes the pain but "craves" it when in heat because that is how the species can continue...as well as the stray problem (i.e. please spay and neuter your cats, people).
That's really all this boils down to; mating and making more humans. Nature will always find a way to ensure that organisms are self-sustaining and don't go the way of the dodo until it deems it necessary. Therefore, to deprive a man of vaginal sex is to go against a drive that is biological and innate. Hence, why I believe it's best for women to avoid dating men if penetration is painful until the problem is fixed (if it can be fixed).
Bonus material on barbed cat penises. Talk about "painful mating"
