Your doctor may be working a side job simply to avoid treating their school debt like a mortgage. You can opt for a 25-year repayment plan, but with some hard work and discipline, even the higher balances can be eliminated by most doctors in less than a decade.
Perhaps what they really wanted to do in life didn’t translate well to an actual career. That’s where the side hustle can come into play.
The doctor job pays the bills and then some, and can also provide the seed money for any number of unrelated pursuits.