This seems awfully US centric.

Well, Western-developed-world-centric, true.

In dynamic economies (e.g. China) you probably would want to start a business. In stagnant and poor places your first priority should be to get out.

aim at "higher middle class", not "rich bastard" category

Going into finance or law can propel you into the "rich bastard" category.

Medical doctors are paid well in many places other than the US, though not as well as in the US. (For that matter, most other well-paid jobs are better paid in the US than anywhere else. Software development, law, senior management, etc.)

Also, though of course this was no part of the original question, medicine offers more confidence than most careers that your work is actually making the world a better place. (Which may not actually be the right question to ask, of course -- what matters is arguably the marginal effect, and if you're well paid and care enough about people in poor countries you may well be able to do more good by charitable donations than you ever could directly by your work. But it's a thing many people care about.)

I think that's intended. Trying to achieve greater wealth generally involves much higher risk, and even if it offers a higher expected value in terms of money, the diminishing utility of wealth probably makes the expected utility of, say, creating a startup, lower than just pursuing a middle-class career that matches your skills.