The barriers to entry are high: 4 years of undergraduate education, 4 years in med school, 3 to 7 years of residency. Those years are very expensive, with the average med school graduate student piling up $250k of student loans. And if you've ever watched a friend go through med school and residency you'll know it's life-consuming; they are immersed in work and miss out on years of socializing and culture. The payoff at the end had better be commensurate or nobody will be a doctor.
You can become a doctor of anything useless to society. It's expensive to become a doctor of medicine in the USA. The system is broken. Where I live, these practitioners make much less and their education was paid for by the state. Their salaries are much lower.
Those years are very expensive, with the average med school graduate student piling up $250k of student loans.
Which, is turn, makes the healthcare industry extremely expensive in the US compared to just about any other developed country on earth. Add to that health insurance company profits and insane medicine prices. Very broken.
Also doctors eat a lot of shit from patients. I think they all deserve a 100K raise just for listening to antivaxxers throughout the COVID pandemic. Imagine the emotional energy it takes to hear someone accuse you of withholding the "right" treatment (ivermectin) while their family member is in a bed with their lungs stiffening on ECMO and could have been saved with a simple shot. Watching the world devolve into social media driven intellectual rot should is terrible.
The question should be why does everyone else make so little. Seriously, if $350,000 is the expected pay after up to 12 years of higher-education and residency, then someone with a 4-year degree should be making about $110,000, which would be slightly double what minimum wage should be ($25 an hour) if it kept up with cost of living and inflation. This is what a prosperous country should expect.