Despite our best efforts, some of us music directors do not plan our repertoire far enough in advance to wait for shipping. I’m sure I’m not the only one who would gladly pay 2 or 3 times the price of a printed copy in order to get a PDF download. Since that would not require printing or shipping, the margin on that purchase would be remarkably higher.
Music is information. Music is not paper. Information moves at the speed of light.