Soundwave on 24 August 2012
Erm, lol, to give you a serious answer, it's most likely a biological imperative.
If the survival of the human race was dependant on men who only mildly interested in sex now and again, our ancestors probably would not have survived to this point through cataclysms like the ice age along with things like drought, natural disaster, plague, etc.
The fact that men are fairly prolific (lol) at wanting to spread their seed likely has allowed our population to continue to grow past some of the extreme hardships humans probably lived in hundreds/thousands of years ago.
