Time to change the voting age to 21.
Agreed. But how about a few "Heinlein" wrinkles...?
First, age for DRIVING, voting, guns, tobacco, lottery tickets, and alcohol goes up to 26 (the max age kids can stay on their parents' health insurance).
Second, exceptions: serve a successful 3-yr enlistment (honorable discharge) in the military and you can do all the above at 21 (longer enlistments would qualify for the exemption at the 3-year mark; officers are not generally commissioned until 21 (or so) anyway, so they could get the exemption granted upon successfully completing the respective service's initial officer training). Peace Corps or other "national service" would not count.
If parents complain about the driving part (too burdensome for the parents), then maybe our permissive parents will start acting like parents and start parenting our little brats in being responsible young adults.
--- End of line (MCP).