Because it is probably hard to isolate the applications for each behaviour from each other. “Compete with A and mate with B as much as you can” is much easier to encode than “Compete with everyone, but then maybe at some point switch to mating with however you are fighting (but be careful that they don’t take advantage of it)”. You get the prisoner’s dilemma at the very minimum.
PS If you think about it, even in humans, who do have sexual differentiation and are capable of very complex behaviour, those behaviours are not perfectly isolated, and external aggressiveness often leaks into the family. For me it is almost out of the question that such careful delineation could exist among primitive hermaphrodites.
Hmm, I guess I don’t really see why that’d be unstable?
Because it is probably hard to isolate the applications for each behaviour from each other. “Compete with A and mate with B as much as you can” is much easier to encode than “Compete with everyone, but then maybe at some point switch to mating with however you are fighting (but be careful that they don’t take advantage of it)”. You get the prisoner’s dilemma at the very minimum.
PS If you think about it, even in humans, who do have sexual differentiation and are capable of very complex behaviour, those behaviours are not perfectly isolated, and external aggressiveness often leaks into the family. For me it is almost out of the question that such careful delineation could exist among primitive hermaphrodites.