Any body can cum from getting fucked in the ass, if a dude fucks you in the ass and knows how to apply pressure to your prostate you can cum out of your cock although massaging your cock could help you to cum faster, when you fuck a woman in the ass you can actually touch her g spot and give her an intense orgasm, i guess you need to work on your ass skills.
Well clearly I don't have the same skillz you have, stud. And I can't say that I've been on a mission to make a dude cum from getting assfucked or having myself cum from getting assfucked, so I'll bow to your experience on the subject.

Not to mention, that I havent tried to push my cock though my wifes intestinal wall into her vagina to try and touch her G spot. The only way I know how to hit it is through her vag, and frankly, we don't have anal sex all that often so It's not exactly my mission to try. Anal is ok but I'd much rather put my cock in my wifes vag, kthanx. Anal is a lot of prep time for the female and my wife isn't super into anal, so it's not all that big of a payoff.