Just because you're not getting into low-level hardware interrupts or vector tables or memory addresses, does not mean you "don't know how to use" a computer. I'm glad you have that knowledge, I enjoy stuff like that too.
But a lot of kids are "really good at facebook" and use that as inspiration to get into web dev. They want to create the next social network, or the next cool website. Maybe it sparks their interest in big data, or databases, or the math behind social networks.
This is just one example. I don't particularly care about or use facebook personally. But there are a million different facets to computing.
Maybe they end up as a graphic designer for a video game.
Maybe they learn they enjoy the machines themselves and build one some day.
Maybe they learn they don't quite care about computers, and just learn to become literate in an essential tool of the Information Economy. That's good too. shrugs