As much as moral conservatives would like to idealize abstinence as the answer to all sexual health issues—because we all know you become universally invincible to an STI once you get married—the simple reality is that it is not the cure-all they have wished it to be.
The bottom line is human beings like sex. With youth comes puberty and with puberty comes hormones. Have we forgotten about the basic biochemistry of the body that naturally drives us to want to procreate — i.e. have sex?