Not sure if I do anymore, but I'm pretty sure when I was 20 years old I still looked about 16, and when my brother was 16 he looked 21. That IS a good point about possibly being less exposed to the sun when being an introvert, and maybe coming off as less socially mature when having less experience around people? My sister always got carded because she refused to wear makeup and is barely 5 feet tall. I also have a theory that I get carded more frequently when I wear a baseball cap, as that is often akin to the college kid's uniform. Got a few grey hairs coming in now, so I'm not sure anymore.