The feeling that most teenagers have due to one specific reason. Our mental evolution has outpaced our societal evolution. It was only a couple of generations ago that teen angst would not have been an issue because the teens in question would have been out working their little asses off picking cotton, hoeing corn, slopping the pigs, etc. These "high schools" we have are just a holding pen for kids who do not need to be spending so much time thinking about life. Life used to happen; now it is a theory.
It's like the joke about the consultant who looks at something that's working great and says,
"Hmm, I wonder if this will work in theory?"