Why can bands play for hours often utilizing different instruments without ever looking at sheet music, but orchestra musicians always read from sheet music?

Question

I saw a clip where a pianist was playing and someone was turning her pages for her, but they fumbled and dropped the sheet music. The pianist kept on playing, but it got me wondering why have the sheet music if she knows the song anyway. Do they really need it? Why can’t they just learn the songs like all bands do?

In: 5311

Answer 1

Bands often play more or less the same music at every concert, while orchestras have short runs of pieces and then go on to something else

It doesn’t make sense to have 100+ people memorize 3 hours of music for a concert they’ll probably play less than 10 times. It does make sense to have 5 people memorize 5 hours of music they’ll play for years

Btw, if you look at concertos, most soloists do memorize their part and play without sheet music, but they can afford to do that because their part is the big important one and they have to practice it a lot before the concert anyway, unlike the rest of the orchestra who can sightread most of the piece perfectly