Just why investment bankers and traders out-earn, say, doctors or computer engineers is a question I've never heard convincingly answered. Are they smarter? Unlikely. Do they contribute more to the economy? Questionable.The difference is easy to explain - being an investment banker or trader is RISKY. These are very smart people that could probably be doctors or executives or any number of other highly paid profession.
But they wanted a shot at the big time, but that shot comes at a risk, make a mistake and you are ruined - probably forever. A doctor, on the other hand, has a pretty good idea what he will make simply by choosing his specialty, the risk isn't all or nothing - it's very good or fabulously good depending on his skill.
It reminds of an old joke:
"What do you call a doctor that got straight Ds in med-school?"
HatTip to A Stitch in Haste & Rolling Doughnut