How does this theory explain the act of crying in private?
The theory explains why someone would want not to cry in front of people (loss of prestige/dominance), but not why someone would want to cry alone, in private.
The theory explains why someone would want not to cry in front of people (loss of prestige/dominance), but not why someone would want to cry alone, in private.
So one answer to your question is that you never know if someone will come by and look at your face in a few minutes.
Adding in an extra check that says "if (someone is watching) { ... do this signaling thing ... }" more costly than just doing it.