Sincerity in rock first started in /lit/ before rock. Like Catcher in the Rye and Holden Caulfield shitting on everyone for being "phonies". Then Rebel Without a Cause, and James Dean's character just keeping it real and not giving a shit about the cool kids in that movie. And then he won over the girl when she saw how real he was. Every guy suddenly wanted to be that dude. I guess that ideal lasted for about 50 years. It's easier to just hide and make a mockery of life.