How could two persons who know each other to express that they really have nothing to share?
The mutual knowledge is acquired during a long time spent together. Only inside a long duration it can be created a relation of familiarity which is not bothered by questions about its nature. It counts as a perfect knowledge, since we know better the things about which we do not put any question.
Differently, the intimate knowledge between the sexual partners might be read as a continual, mutual investigation and it cannot give birth to the feeling of familiarity without the help of time. Therefore, two former sexual partners can express easily their distance after a short time spent together.
On the contrary, the mutual knowledge impedes a rough formulation of the distance between two persons. As a consequence, they prefer to keep the distance concealed beneath a great amount of words about some subject matters which are indifferent to each of them and never put their relation at stake.
Even if it is generally not recognized, the time reveals many couples of simply talkers beneath some long and living conversations. Those talkers were formerly lovers, parents and children, or friends.