Via the ASI blog, its daily blog review always a source of good stuff, I have come across this explanation of why Valentine’s day is rational from an economic standpoint. No. 4 appears to me to be the most convincing:
4. Rationality as counter-signalling. If a woman is looking for commitment, she’ll not want a narrow utility maximizer, because such a man will leave her the moment a better offer comes along.
The prospect of being traded in for a better model is the source of most people’s insecurity in romantic relationships. I speak from experience as a maximizer of utility.