Rational players coordinate on any available signals beyond game mathematics. [causal]
What the players need is some signal to coordinate strategies; if they cannot find it in the mathematical configuration of the payoffs, they can look for it anywhere else. And strategies may occur in such fashion, or with such labels or connotations, as to provide a potential basis for ordering them or sorting them that rational players find useful.
Thomas C. Schelling, The Strategy of Conflict, loc. 678