I have been paying attention to this for awhile. The build up is great, waiting , wanting. The feeling during is epic. Then bam job done. You don't feel depressed, nor do you feel you have accomplished anything amazing. You feel kind of empty inside :p quite literally tho. Like the time could of been spent doing something more productive. In the meantime while the female groans about on the floor or bed enjoying her orgasms and passing out. Your there thinking perhaps go make a sandwich or watch a film. 20 minutes later your ready for the same experience without a care. Masturbation just resulting in the same result..
My therom is that it's so the man can defend the female while she's trembling about unable todo anything (unless she is a feminist which case ofc she probably didn't orgasm and can ofc defend herself..) from predators or other cavemen whatever. All in all , without the multiple orgasmic vibe , I think men got a pretty crap deal on sex.