That's especially common with jazz. Lead sheets are just a bunch of chord symbols and a melody, and if you're in the rhythm section you're not playing the melo

That's especially common with jazz. Lead sheets are just a bunch of chord symbols and a melody, and if you're in the rhythm section you're not playing the melody anyway. Someone counts off the tempo and you just go. Not to make jazz sound easy; jazz theory is way harder than any of the classical theory you'll learn in college music classes (speaking as someone who aced all the college music theory courses and just can't seem to get a handle on bebop).