Age to be US President - 35
Age to be US Senator - 30
Age to be US Rep - 25
Age to Vote - 18
Age to Drive -16-18 Depending on state
Age to drink - 21
Age to get full social security 65-67 depending when you were born
Age to get pilot's license -17
Age to get commercial pilot's license -18
Age to get ATP license - 23

Which one is not of these is not government mandated? But it's ok to discriminate in these situations?
Is a 20 yr 10 mo 29 day old really not mature enough to drink but add a day and then it's ok?? There is always going to be "some" type of discrimination.
Just as there are some 60+ year olds that would be fine in the Capt's seat, and some 50 year olds that should have retired already; society must find an age that can be accepted to define when someone is or isn't fit to hold some position.