For that matter, the HPV shot is not recommended for adults, since most of us have probably already been exposed (unless, again, you're a nun.) It's only recommended for pre-adolescents, under the likely true assumption that the majority of them will NOT be celibate.
Actually, it is recommended for adults, at least up here in Canada. It's currently approved for men up to age 26 and women up to age 45.
It's recommended and highly desirable to administer it pre-teen, so as to get maximum protection, but even for sexually active persons, it will still give at least partial benefit, as even if you have had an HPV infection, it's damn unlikely you'll have contracted all four strains the vaccine protects against.