"So, why do physicians pay for 4 years college + 4 years med school, and live with $40,000/yr incomes for 3 to 7 years of residency when INSTEAD, they could be chiropractors and pay for just two years of schooling and spend the rest of the time making a high income?
Clearly MDs are NOT in it for the money."
You left out the part of a lifetime of very high income after all that. By the time they are 30 years old they are making six figure incomes. Add that to your above equation and then tell us money is not involved.
It is unclear here if you are refering to MDs or to chiropractors!