Men let themselves go after marriage. Put down the beer, get back to the gym and chase your woman like you used to! If you don't put the effort in, what do you expect?!
I have no idea. But if you find out, let me know.
Most women aren't interested in sex in any meaningful way. In western society there are roughly equal numbers of men and women and there are loads of horny guys looking for sex. If women were as interested in sex as men were all those guys would find getting laid quite easy. As it is there is such a shortage of sexual partners that men will, and often have to, pay a lot of money, hundreds in fact, to a woman for an hour of sex.
Now if anyone can square this with women having a sex drive equal to a man's, accepting the statistically few exceptions, I'm very interested to know how you've done it. If it is the case that male and female sex drives are equal then there are A LOT of very sexually frustrated women that conversely feel no need to do anything about their sexual frustration.
So the answer to this is simple, women won't have sex because they don't want sex.
I wish I could answer that question and make alot of people very happy. I've been living in a sexless marriage for quite some time now and not by my choice. It was her who said I no longer have any desire for sex. I gave up begging, whats the point? If she doesn't want to have sex and you put pressure on her to have sex, it just won't be very good. Most women quit having sex for various reasons, usually no desire, hormonal, or no attraction to spouse any more.