Even with doctors, to be solidly in the above $200,000 layer, you pretty much need your own practice established and smoothly running (with nurses, staff, and everything) -- not every M.D. out there has that, and the effort required to get there is equivalent to the effort required to start your own business (with 80-hour work weeks etc.)
And that school is very expensive. Also, many highly-paid positions carry the risk of getting sued by the patient's side for having made a silly mistake (can happen to anyone) or even for things that were unavoidable but which the patient's side believes otherwise.
What % of doctors have an impact on the health of their patients? Almost all.
We are dealing with statistics here.
You know, a big part of the prosecution's evidence in the Casey Anthony trial turned out to be false; it was due to faulty software. She could have been imprisoned due to a software bug! http://en.wikipedia.org/wiki/Casey_Anthony#Evidence
Now consider that anybody can call themselves a software engineer without even picking up a book. Next time your life hangs on the proper functioning of some computer system, think about that.
As for the remaining percentage of people, we may not deal with their physical health, but our work can impact their financial or family's well being fairly easily. Some of the code I have written has touched billions of financial transactions that have decided the future of whether people will be able to buy a house, or a car, or any other line of credit.
Not trivial.