Why is 18th birthday important in the united states (n other countries too)?

i'm not from the US but now i live here and i've seen a LOT of people (basically my friends) celebrate their 18th birthdays with much pomp and joy!...why?...i mean what is SO important about this age that people call it a "milestone" in a person's life?...what are some things/benefits of being 18? show more i'm not from the US but now i live here and i've seen a LOT of people (basically my friends) celebrate their 18th birthdays with much pomp and joy!...why?...i mean what is SO important about this age that people call it a "milestone" in a person's life?...what are some things/benefits of being 18?
9 answers 9