Age of dependence.

I wonder why the age of dependence for so many things are so different. In order to be considered old enough to drink you have to be 21, but you only have to be eighteen to smoke. Too laugh at that to get tried as an adult in jail you only have to be sixteen. For FAFSA you are only independent when you are 24. Other for FAFSA you have to have a child or something. So im old enough on my taxes to be independent but not to apply for financial aid. Funny