Composers write music whether other people hear it or not/buy it or not. Writers write without needing readers. They set their thoughts down because they have no choice. That is what writers do. Their performance is not contingent upon having readers. But isn't an actor's performance contingent upon having others view what they do? You can write alone, compose alone, poeticize alone but act alone? Reaction is what an actor strives for. Without it where is the incentive to perform?