I used to believe that almost nobody was really interested in anything. This was because (a) I had never been really interested in anything and (b) "Passion" was a mandatory signal, required for getting into college. When I saw people who appeared to be genuinedly interested in things (sports, music, running the school newspaper, building robots, whatever), I assumed they were just better than me at sending the required signals. When I got to college and saw people who continued to appear interested in these things, even though extracurriculars were no longer valuable, I realized I had been wrong.