What other incentive is there? There might be some willing to go deep into debt in medical school so they can work for free out of the goodness of their hearts, but that's a vanishingly small number of people.
And yet apparently countries all over the world have to artificially raise the bar for med school because so many people want to be doctors for incentives aside from just the money.
People don't go bankrupt at anywhere near the rate Americans do for medical reasons. People don't constantly bring up dealing with insurance as the #1 burden during medical procedures.