system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why haven't humans developed a simple and clear signal of romantic interest? The vast majority of animals have some form of mating dance/call/thing; why did humans lose/not have this?
gpt
So much of human behaviour and communication is cultural/memetic/linguistic rather than instinctual and deterministic, so instead of a single dance/call/song/thing we have thousands and the meaning depends on cultural context.

On the other hand, we have all kinds of subtle physiological cues to indicate attraction and arousal.  Many of these are conveyed subconsciously, but some people become more skilled at actively identifying them.