These days women are picky because they have the ability to create a wonderful life for themselves without a man. Although many women would love to share this great life with someone special, it's optional, not essential, to have a man in order to be safe and comfortable. So a guy has to be pretty fantastic to get anywhere near a modern woman.
Luckily, the ideal man looks different to every woman. In most cases it's just a case of putting together men and women who are looking for each other's unique profile. That is why dating services and dating websites have such great success for people looking for long-term relationships. Women can be as picky as they want because they are drawing from a huge pool of potential partners.
Men have to accept that women will want them to show certain qualities and abilities before deciding that they should invest the rest of their lives, and those of their children, with one guy. Women have far more to lose than men if they don't choose wisely. Even when available men are scarce, women still need to consider their decision carefully.
In biological terms, a woman has far more to lose than a man if she gets hooked up with the wrong partner. She needs to make sure that the genetic code she is giving her child is the best one she can find. Our basic biological drive to reproduce lurks under the surface of everything we do.
Once she becomes pregnant she's investing her physical resources into a child with this man for a year or more. Once the man has impregnated her, he can go off and impregnate multiple additional women in that year. This imbalance means that the original choice of partner is much more critical to the woman.
If the man is not so hot physically, but has other resources to offer like money, intellect, social position, or citizenship for her and the child, this may compensate. It certainly explains why you see powerful men of all shapes, ages, and sizes with gorgeous young women.
Once women get older and are no longer capable of having children, they still need to be careful about which men they partner. All the social pressures that women face do not disappear with the ability to reproduce.
The drive to get married and stay married are still alive and well in today's societies. Should something go wrong with the relationship for whatever reason, statistics show that generally divorced women and their children must accept a much lower standard of living, whilst divorced men retain their position. As women still make less than men, and must also arrange child care, they are unlikely to find work with high enough pay to make up the difference.
For both sexes, there is a great advantage in teaming up with a partner and working together to create a secure and happy life. The wrong partner can mess up a person's life and condemn them to years of rebuilding. Women are also stigmatized far more than men if they have been divorced, and usually retain primary custody of children, so finding a new partner who can accept her situation and love her children becomes difficult.