This is a paradox mostly for teenagers and young adults.
"We ignore those who adore us and adore those who ignore us".
Maybe it's because they don't think love is worthwhile unless they have to "earn" it or "win someone over". It's not uncommon for girls who are going through a "bad boy" phase to shun the "nice guy".
He's "too nice".
I've often said you could stick such a woman into a room with 5 guys and have four them on their knees extending their heart out towards her while the fifth guy sits in a corner sipping on a cocktail acting like she doesn't exist. That will be the guy she wants to get to know!
She sees him as being a challenge. He's a man of mystery. She wants to prove to herself that she can have him too. Odds are she'll step over the four other guys to approach him. If she learns other women want him his stock rises even higher. The "bad boy" never lets her know where she stands with him. Feelings of insecurity and drama intensifies her love for him. She'll bend over backwards in her efforts to be "the one" he loves.
It's not until she's had a series of heartaches that she decides to "settle" for a nice who adores her. However he'll never receive the kind of passionate love she offered the "bad boy".
He's "Mr. Good Enough". It's her turn to control the relationship.
"Never love anyone who treats you like you're ordinary."
- Oscar Wilde
Once women and men reach a certain age they become more selective with regard to whom they spend their time with and open up their heart to. They evaluate his/her traits before committing.
During their youth they really didn't have a "mate selection" criteria.
They allowed "impulsive connections" and "happenstance" to dictate their relationship choices. That's the equivalent of going shopping without a list! With age comes wisdom.