Though the whys are highly speculative since speaking from an evolutionary view point there is no designer or creator running the show, at least from this evolutionary perspective that is.
From an evolutionary perspective its easy to understand why males climax - to deliver sperm for reproductive purposes and the associated good feeling seems to make it a joyful experience so we will continue to reproduce. The warmth of a close and intimate relationship also contributes to the reproductive will of our species, Getting lost in sexual activity is wonderful on a psychological level.
Some evolutionist believe it (female climaxing) is an adaptation that has developed in order to maintain the interest of a mate, making him feel like hes satisfying and therefore useful.
I can certainly see that perspective and sounds like a reasonable assumption to me and may be correct. But I've been thinking about this and have of course another idea that I think is feasible to consider (and it has nothing to do with autism, Peg

Now, I'm not bragging or anything but hey, what can I say, I'm 53 and she's 50 and we're still going pretty strong.
What are your thoughts? Also, any perspective is welcome, not just that of evolution.