I would estimate that around 90% of the people I know who want to become a doctor (around 30 people) are motivated solely by the desire to make lotsa money and be able to drive an expensive car. Just saying, I don't think you can easily divide ambitions into "good" and "bad.
There far easier ways to go about getting more money than spend over a decade in studying for it, plus all the hard work that comes afterwards.
More people that get into medicine that I know of either are idealistic, like the lifestyle (as portrayed on TV), had parents that were themselves doctors, or do it for the prestige. The money is not the biggest factor.
In finance you can be very dependent on the market conditions, same in law (without a lot of business activity businesses don’t need to consult lawyers), in research you are also very dependent on the hype around your field to get grants, starting your own successful business is brutal if you don’t find the right opportunities or network of people, engineering is no cake walk of study either (especially adding in the work to stay relevant in the field) and joining a startup for good money is absolutely not a secure employment.
There will always be a need of medical personel however and since it requires a license given out by a few institutions you can be sure that your field will not be oversaturated, especially as it’s hard to obtain said license through study. Again, not saying it is easy becoming an MD, but if you are a competent person the path to a secure, good paying job is clearer if you choose med school than engineering, law, graduate or finance.
It is, but it also has a much smaller earnings cap than other professions. So "for the money" here means "for decent enough money but nothing to write home about".
And depending on the country surgeons in specific fields can make obscene amounts of money. Neuro surgeons have a median salary of almost $600 000 in the US and to earn that much money as an engineer you have probably co-founded a successful startup or become an executive.
Old good "follow your passion"?