They are deeply involved in the thrill of the hunt as a key part of the experience.
Or they may fear losing themselves in a relationship with a partner who would require too much attention without their own needs being met.
They may have suffered through a troubled childhood experience that has wounded them or they now have higher priorities such as their career or taking care of a sick parent.
Perhaps, they are recently divorced or widowed, and legitimately not ready to get involved in an intimate relationship.
Have you ever met someone who "romantically" knocked you off your feet -- as in "Hi Mom and Dad...
you're not going to believe this, but I just met the man of my dreams! How did they miss the obvious warning signs before they became intimate and gave their heart away? " or "He wants the same thing I want: to settle down and have children.") For those of us who've been in a relationship with an emotionally unavailable person, we know the pain of not being able to get close to the person we love.