I played trombone and that instrument was full to the brim with spit and a good toot would send droplets flying everywhere. So catching that all with cloth isn't the worst idea in the world.
I can see it with a trombone since you are blowing directly into it, rather than across the top of of a flute mouthpiece. On the other hand, the flute end is probably right next to the next band players ear.
I played trombone and that instrument was full to the brim with spit and a good toot would send droplets flying everywhere. So catching that all with cloth isn't the worst idea in the world.
I can see it with a trombone since you are blowing directly into it, rather than across the top of of a flute mouthpiece. On the other hand, the flute end is probably right next to the next band players ear.