I believe that a physical level, and not specifically a sexual level, is the first level of communication between men and women (and between men and men, and women and women for that matter). Many prejudgements are made based on the initial physical encounter between any two people and early communication is based upon those prejudgements.

When the encounter is between a man and woman the prejudgements are quite often sexual. Given this context, a sexual communication level seems almost inevitable. Unfortunately for many men (and women) this level of communication is sufficient.