Men only buy their own underpants when they are hoping to entice a potential partner into a relationship, according to a recent survey. The poll by British retailer Debenhams showed that men normally leave the purchasing of their underwear to their mothers until about the age of 19, relatively late when compared to women, who start buying their own around 13. Between 19 and 23, men tend to buy their own underwear, up to 31 pairs a year, in the belief that wearing new underpants is an essential prerequisite to a relationship.