It's been said that the most powerful urge is to mate and procreate -- continuation of the species and all that. I believe that the most powerful and persistent *human* urge is true intimacy -- the ability to let down our defenses and simply share our existence with another human, who will accept us for what we are and where we are, and love us at that point. The drive to find this other person to share our being with (I think) surpasses our other needs once we get past the basics of food, shelter, and clothing.
True intimacy -- absolute unconditional acceptance of another in every way -- will result in the kind of physical intimacy that *can* be expressed by sexual activity. The problem is that many people try to shortcut the necessary work of discovery and acceptance of the other person by jumping straight to the sexual intimacy. Without the effort of discovering what the other person is all about, the work of addressing one's own feelings during this process, and the dropping of one's defenses to accept the other person -- the intimacy that results from sex isn't fully appreciated and falls short of expectations.
There are too many shallow people around who are willing to substitute quick physical sexual activity for true intimacy. The real reward in a relationship isn't the sex, but the deeper kind of intimacy. Granted, sex appeal is an aspect that will always be present, but in order to really enjoy it both parties have to know, understand, accept, respect, revere, and love the other person.
