There are 31 states that allow parents or guardians to give alcohol to minors, only 7 of those restrict it to a private residence. Even in countries where there is not minimum drinking age and it is customary for teens to drink during meals or religious ceremonies with their parents, there is still an observable incidence of intoxication and binge drinking.
Some parents have the idea that allowing their teenagers and friends to drink in their private homes as opposed to attending unsupervised parties is a safer alternative. However, adults can end up legally liable or even in jail for supplying alcohol to other people's children.