I'm 27 and I still get ID-ed all the time for 18+ venues. You might have to live with being questioned for awhile as annoying as it may be.

To be honest, you and other people in their late teens are way more capable and able-bodied to help in an emergency situation. It's the seating of 70-year-old-men-with-canes in exit row thing that I don't understand.

Either way, if something happens to the flight, we're all out of luck.