I think it is a huge waste of time and money. If you either have business sense or you don't, it is not something you can teach. You can teach the laws of business but that is no guarantee for success. I think you would be better served working harder in your regular classes and working outside of the classroom, than getting another degree.
The one advantage I can see if you wanted to open your own practice right out of residency. But even then, you'll learn more in your residency and your first year practicing than you will ever in those dumb classes. Maybe people do it for the pride or b/c they don't have enough letters after their names?