Why are so few developers trained in health sciences (health care)?

Looking at the "Undergraduate Major" section of the StackOverflow 2019 developer survey, we see that 0.3% professional developers were trained in "health sciences (eg nursing, pharmacy, radiology)". Why is this the case?

In the United States, health care will account for almost 20% of GDP in 2020. Given such massive spending, should not there be more developers with health care histories?

Do those who leave health care to enter the technological space do not identify as developers?