Of course, many of us simply approach sex as a means to pleasure (excepting tantric practitioners).
The pleasures of sexual activity (including intercourse, masturbation, fantasy, pornography, etc.) can become so, uh, seductive that we sometimes lose sight of ourselves and the other.
And perhaps that's where sexuality crosses the threshold between need and want: when our primary motivation is "to lose sight" in the throes of pleasure.
Once we cross that threshold, our world can become sexually saturated with public and private obsessions.
These obsessions have a function: to take us away from the feelings, impulses, and fears of the moment - the what is of life.
It can feel intolerable, being with life as it is.
In those times, what would it be like "not to touch" obsessive sexuality, either literally or in the mind, and simply stay with our anxieties, urges, dreads, and afflictions?
Perhaps sex might again become a simple and joyful need, without the compulsion of desire and wanting. Could we try that?