Homo economicus is a poor model of human behaviour. Per https://en.wikipedia.org/wiki/Homo_economicus#Sociologists https://en.wikipedia.org/wiki/Homo_economicus

Homo economicus is a poor model of human behaviour. Per https://en.wikipedia.org/wiki/Homo_economicus#Sociologists https://en.wikipedia.org/wiki/Homo_economicus#Sociologists, both neurobiological and anthropological research suggest that unsolicited gift-giving is a natural human behaviour.