The real reason. Dating is based on value. People assign values to each other and how we perceive whether someone is on our level or higher is based on behavior, wealth, looks, social status; we do this with materialistic objects so why not people.
Women are hypergamous meaning they only want to get with a man they deem better than them. When a nice guy meets a woman he often tends to use niceness to try and win her over and show to her that she is special but this does not translate to the female brain as such.
Before having sex a woman perceives a man doing nice things for her as him trying to bargain with her on why she should give him a chance. Obviously if your bargaining with someone the person who you come to has the higher ground and therefore higher perceived value. Thus, a woman in such situation will reject the nice guy advantage because hypergamy dictates you must be better than her to get those panties.
The only case this does not hold true is when there is such a large contrast in looks, social status, money in the man's favor that him being nice does not hit his chances with the woman. The reason for this is because he has enough self evident things in front of him that the woman perceives him to be of higher value to her and him being nice comes from a place of generosity rather than a place of sucking up the female's minds. Such men women often refer to as GOOD MEN.
Thus, the reason nice guys fail is because women perceive kind acts as a way of sucking up rather than actual being nice to them (this is before sex). After sex the woman has given her investment and if a man continues to be kind to her then she considers just that because she believes the man has gotten what he wanted from her yet still persist with kind gesture so he must really be a nice person to her.
Most Helpful Guy
Its not the only factor.
It's a factor.
Most 'nice guys' are trying to follow outdated dating models that came from a time where men had real power over women. Men didn't have to do all that much to demonstrate that power. Rather they needed to show they were benevolent with the power.
In the west, those days are gone, and doing too much seems subservient and needy.3