Why men are single
Men are single for many reasons. One of the reasons is the lack of attraction to someone, if he didn't commit it means he hasn't met some he loves. Some men never marry because they loved someone before and got rejected, so it's hard for them to trust or love again.
Some men fall in love easily, while for others it's much harder.
Some men are still in love with a woman who rejected him before, so he isn't able to fall in love again because of his heart attachment.
If a man is or was in a committed relationship but never married, he probably just doesn't love that woman very much. When a man is in love, he will do anything to be with her, even marry her so he wouldn't loose her.
Other men are single simply because they don't beleive marriage will make them very happy. If the were sure marriage will make them happy, they would do anything to make it happen. Lack of his belief make it harder for him to pursue it.
Men who never got married
As a man gets older and older, he realizes that he doesn't really need anyone and he doesn't need to be hurt again. The older he gets the less belief he has in beautiful love and happy marriage.
Women often are comfortable to get married even if they aren't very sexually attracted to a partner, but for men attraction is much more important.
If a man has hard time to get sexually attracted or emotionally attracted to a woman, then he won't want to marry. So, if he doesn't want to commit, then you aren't "the ONE" in his mind.
Even if you wish you be the one, you just can't change how he feels or what he wants. Only he knows what he wants and no matter how much you want it to be different, sometimes you just have to accept him the way he is or walk away.
It would be nice if you had the same wants and desires, if you were both alike, but sometimes it can't be everything how you want, dream and expect.
Some men have committeemen issues without realizing why, they just do what feels right to them. And what feels right for him doesn't always feel right for you.