The average teenage girl loses her virginity at 17.3 (17.0 for boys) in the United States, but the age at which it becomes a stigma can vary among subcultures, religions, and even schools.
Reasons ranged from fear it would hurt, anxiety about pregnancy and STDs, and a five-year illness until the reason was simply virginity itself. Why give it up if you've waited so long? Plus, sometimes the fear of revealing virginity after a certain age becomes a fear itself.
Most people have an age they don't want to reach and still be a virgin — what was, or is, yours?