It's epidemic, and not just with teens, it's the adults too. Cannot count the amount of times I've heard a full-grown man say, "That kid/guy must be strong and athletic, look at his 6-pack." Abs have apparently become the new indicator of strength and athleticism.
Related to this, when people see me or my son pushing sleds, flipping tires, tossing med balls, carrying odd object, they automatically assume we do CrossFit. It's not worth my time to explain to them that these exercises were around before even the barbell was invented.