it's customary for married couples to give out ang pao (hong pao) because 'married couples' are considered adults.\nang pao signifies 'good luck' & 'may you grow up asap'...\nin the 1960s & way way before that, majority of the chinese are poor people or peasants. so, during chinese new year, the adults gave out ang pao so that the unmarried adults may have good luck in love or career (or good harvest) , to get married soon. then they gave children ang pao, so that they can grow up strongly & taller for that year, & join in their parents to work in the fields.