If I have made an appointment with you, I owe you punctuality, I have no right to throw away your time, if I do my own.
Actually, most things I say in public lead more or less directly to my own compositional practice, so I should be careful about generalizing lest they come back to haunt me.
In Irish law, busking is considered vagrancy - you can be arrested for it. It's risky asking people for money in public. So it's not like it's a high-art job. And people who do it as a high-art job make very little money.