It's illegal to photocopy copyright-protected music.
You all do it anyway. You have been doing it since long before the rise and fall of Napster.
You don't do it to steal it.
When you photocopy a score, the vast majority of the time you are making copies from a score you already own. You make photocopies to avoid lugging around a pile of heavy books when all you need is just a few pages from each one. You make photocopies and put them in a binder to make it easier for your accompanist to turn pages. Maybe sometimes you even use a scanner to make digital copies of songs and arias so that you can email them to a colleague, which is much faster, cheaper and safer than packing up a score and mailing it (not to mention decreasing your carbon footprint).
But rather than asking how they can meet our actual needs and turn a profit at the same time, the music publishing industry continues vehemently trying to put a stop to all this.