That experience made me think about how men interact with each other under many conditions, and I realized that there are unspoken, but still rigid and powerful, guidelines that govern how men relate to each other. Men usually speak to each other only for a specific reason, to accomplish a well-defined task. They call each other to order lumber, to arrange a meeting, to negotiate the price of a product, and so on. It's these general guidelines that helped shape the very specific, time-honored, and inflexible rules of behavior in a men's room. This first rule determines all the others.
Men go to the bathroom only to perform their bodily functions.
During that time, the privacy of each man is inviolable. Men do not speak to each other in the rest room. It is forbidden. A men's rest room is like a sacred tomb. Speaking would constitute a social gathering, which would be entirely inappropriate in a place where private bodily functions are the principle goal.