system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do orchestral musicians (violinists, for example) have to read their music on stage, as opposed to rock musicians who have their parts memorized?

Don't say it's more complicated... think of Rush, etc.
gpt
Two reasons come to mind.

First, yes, the music *is* more complicated. Symphonic music is tightly scored, precisely notated stuff which is deeply dependent on exact precision  and unity across the ensemble. Play a note marcato when it's marked staccato and the world-famous guest conductor with the diva complex might well decapitate you—and there's thousands of notes with all sorts of annotation. Rush doesn't compare.

Second, if you're in a professional orchestra, you're generally giving at least one new concert series a week, which means learning at least an hour of this stuff in time to work with whoever is conducting that concert that week, then getting it up to performance standard in just a few rehearsals. This isn't Rush—it's being in a cover band that does Rush better than Rush this weekend, Queen better than Queen next weekend, Bon Jovi better than Bon Jovi the weekend after that, and on and on for an eight-month season, all while trying to juggle your private students, solo recording contracts, and whatever else you do to try to keep your family fed. Memorizing the second violin part to every Beethoven piano concerto takes time you just don't have.