Yeah, it takes an awful lot of willpower or severe shyness to survive abstinence only. Hormones are just so powerful.

The other problem with the abstinence only method is that it tends to be presented in a way that makes sex into a sin which leads to guilt which gets in the way of a healthy sex life when you are ready for it. It also makes sex forbidden, which then increases its appeal to the up and coming hormone monster. Lots of kids who practice abstinence only end up parents.