This is the Catholic "hook" for the sacrament of Confession, and the need for ongoing, continuous association with the organized Church, priests, etc.
It's worked well for 2000 years, precisely because it's such a spontaneously occurring sin among teens, who all know it's a sin immediately - every one of them hides it from the instant of discovery, without being taught to do so. That's knowledge of sin.
And therefore need of redemption.
And therefore need of the sacrament of Confession, often.
You really believe it is a sin? Maybe people hide it out of embarrassment, sort of like using the toilet or having sex in front of people.