From a deep psychological viewpoint the subconscious mind interprets our anima animus states according to our upbringing and role models. Which means that for mate selection a female is using her father image role model, the media image, the literature image, the any other male influence image in determining what her partner selection is going to be. This means that in a psychological level the patterns that are created early on in a woman's life are going to be enacted throughout her life.
When she thinks she finds the right man, the archetype mirror image, she will find out this isn't the case because then once the patterns fall apart and the sub personalities disintegrate into a shared union of wanting to achieve some kind of stability both the father and mother image ego shapes are in conflict with what they wanted in the first place. and it is much easier for that deceptive alchemical process of love to take shape. Especially when they don't need to, both the male and female, discard their ego self and false personalities in order to face their true essences. And would much rather go their separate ways than deal with their ego self and face their maturity. usually if one is willing the other is not and a break down in communication occurs and the relationship dissolves.
This goes throughout their lives and while the ladies struggle with finding the right kind of stability without addressing and learning from their subconscious images, the patterns repeat. And often than not there is a secondary real element here. Its called testosterone and estrogen.
What you will find is that males with high levels of testosterone are viewed as the idyllic attractive entity yeah. The sought after alpha/beta variance. Have you ever wondered why this is so? Because the female brain is wired to accept certain signals that pertain to masculinity as much as a male is wired to accept certain signals that pertain to femininity in the same respect.
And then what you find is that those men who create action, are confident, decision makers, get things done, are doers in every sense of the word, activators of attraction the woman will fall in love with it. This is her safety. Do you know a woman needs to feel safe in order to love. Would it be any different then womens need for sensuality would disappear and women wouldn't require emotional connections to fall in love to have that attachment of loyalty after. And guess what many if not all sensitive nice guys are low testosterone oriented, I would hazard a guess and the smell, the subconscious entity that is the females estrogen signals that there is a weakness, a disconnect somewhere along the line and biologically from the wrong matching of the immune system, there won't be any generated interest but friendzoning.
Because emotional lovers are mirror images of what women have learned is the opposite of what is needed to feel safe and secure to fall in love with. It is their mirroring feminine attributes that are too similar to them to fall in love with. How can this be the case you may ask when lesbians would love each other and know exactly what to do. Because even then there is a feminine and masculine role.
Anyway there is more to it than this. But whenever you hear why nice guys are slapped in the face one too many times its because they are passive and lack the initiatory ability of what subconsciously defines a man in a womans eyes to be healthy and expressive. Like a rooster and a peacock. Without showing attitude, initiative, expression, all the colours of your character before and after the attraction process dies, your authentic self as they say then you flatline. That is what happens after marriage, the emotional gut level attraction that was there, the so called chemistry changes. And then the focus when empty and unfulfilled changed to distance and unloved. When the true colours that have been there all along surface and neither partner is willing to deal with it.
A nice guy would pretty much have to be anything but passive, to show some spine, to exhibit those qualities that create attraction in a womans subconscious level, to demonstrate that you would pretty much be a conqueror, be able to stand up for yourself, have a backbone and fight for her, offer her shade and a willingness to feel comfortable without presenting the complexity of herself back at her as emotional males would do.
Plus there is the 8 stages of intimacy that would most certainly be a requirement to be fulfilling and long lasting. Like so
Stages
And the underlining theme, safety and security, to feel comfortable with their sexuality, to feel connected with their intimacy and trust you with their mind, body and soul as they say. And sensitive males can become as threatening, if not more so, then aggressive males subconsciously. Through the agency of their subconscious mirroring, biological clock and estrogen levels.
That's my take on it. and why I too struggle with relationships.