You hear it all the time from doctors — they would never choose medicine if they had it to do all over again. It’s practically a mantra, with the subtle implication that the current generation of doctors consists of mere technicians.

When I first started in practice, I found such comments both perplexing and annoying. I loved medicine and was excited to come to work every day. I considered those naysayers jaded has-beens, fusty old-timers pining away for the nonexistent “days of the giants.”

However, as the years have passed, the warts of medicine have grown more conspicuous to me. During some of the more stressful days — crushed by impossible time constraints and ever more onerous bureaucratic demands — I can’t deny that the thought of giving up clinical practice has crossed my mind. Life would be so much easier….

Yet, each year, a new wave of enthusiastic medical students floods our clinics and our wards. Part of me always wonders: Why do these students still choose to become doctors?

It certainly can’t be the money — Wall Street is the faster and more reliable route to wealth, as evidenced by the skyrocketing of applications to M.B.A. programs.

Applications to medical schools, surprisingly, have held steady over all, despite an exodus of top students to finance and banking. According to the American Association of Medical Colleges, about 40,000 students apply to medical school each year, with some 17,000 matriculating. (For comparison, there are about 45,000 students starting law school each year, and 100,000 starting business school.)

Incoming medical students, while steady in their numbers, have had a major shift in their demography. In 1970, medical students were nearly entirely white men. Now half are women, and a third are Asian, black or Hispanic.

I recently worked with a third-year student who’d just interviewed a patient with...