One thing I remember from the first Dot-com crash circa 2002 is that the service quality in Silicon Valley area restaurants suddenly got a lot better. There were a lot of former "HTML programmers" forced to find other jobs.
Right - if you ask a heart surgeon to wait tables they'll probably do a great job!
But it's still a waste of their talents and society as a whole will be worse off than if they did heart surgery. You can measure that because a waiter makes minimum wage and a heart surgeon does not - the heart surgeon contributes more to the GDP than a food service worker.
That's the meaning of that metric and that's why it's useful.
