"Any idea why that might be?"
I have heard that the anesthesiologist is the most important person in the operating room since he/she literally holds the patient's life in his/her hands for the duration of the operation. Maybe that awesome responsibility gets to them after a while. The operation could be a complete success, yet the patient could end up dead because of something the anesthesiologist did wrong.
Just my two cents.
It’s stress. More people are killed on the operating table by anesthesiologists than surgeons.
I have a friend who recently retired from the profession. The premiums for his liability insurance were more than $200K per year.