If everyone were trying to maximise their own wealth, we would have no nurses, no-one would be a firefighter, no-one would be police, no-one would work in the military, etc etc. Vast swathes of jobs would have unfillable vacancies because everyone would work them for at most a couple of years whilst living out of their car or similar in order to save, then they'd be hustling and trying to start their own business or get a job in finance or whatever.
I have a fairly solid academic background, and of my cohort, less than half, maybe even under 25%, went into traditionally well paying fields.
Most are more interested in driving academia/science forward or generally on other social goals as long as they have enough to pay for the house and car.
You could equally ask why doesn't everyone lift at the gym 10+ hours a week, or run 50 miles, or aim to learn a new recipe every week, or whatever else. Different people have different goals and that's wonderful. Money is just one of many balls that people try to juggle.