If the band is paid to perform, they should be declaring it as taxable income, right?
If they donate their time, they can deduct their band fees and expenses they would have earned for a paying gig.
If they can and they want to donate their time, great. If not, it is a free choice. Do not get upset.
Every year I walk and collect money for MS. I am SO thankful for donations, but NEVER get upset if someone does not sponsor me.