People cry when they are sad because crying is an emotional response that serves multiple purposes, including emotional regulation, signaling distress, and facilitating social connection. Emotional tears release stress hormones and other chemicals, which may help alleviate tension and improve mood, offering a form of catharsis. Crying also acts as a nonverbal signal to others, expressing vulnerability and the need for support or empathy, which can strengthen social bonds. This biological and social function of crying is unique to humans and plays a significant role in emotional communication and mental well-being.