Residents, that is, physicians in their first 3-7 years after medical school graduation work 80 hours per week. That's less than a generation ago but it is essentially two full time jobs. Of course, you are going to come home after an overnight shift and be ready to collapse. If things went badly because a patient had a poor outcome or you were chewed out by the boss or by a patient's family member, or you feel as if you were in over your head and worried that you may have forgotten something important, you might have a hard time switching gears and being social with your family. If your spouse is under the same pressures as a physician, you can imagine that it can be difficult to let it all go and put the focus elsewhere -- or you just want to sleep when your spouse wants to chat, etc.
Even as attending physicians, you are not likely to have a job that is 9-5 with weekends off. You may be able to go out on a Saturday night but you might feel the need to stop at the hospital on the way home to check on your residents and patients. You might get pulled from the dinner table on a holiday to deal with a patient who needs emergency surgery or who has suddenly taken a turn for the worst.
There are attending physicians who have time for hobbies and family activities but it requires time management and discipline.
With respect to divorce, this paper is old but valid.
http://www.nationalreviewofmedicine.com/issue/2006/03_15/3_physicians_life02_05.html
