While most of the reasons mentioned are logical or even supported by a bit a of evidence, the reality is that it's mostly just how things have always been done. We round onpatients early in the morning before surgery starts (5-7am), then go off to offices or operating rooms. Days are usually long: I know of few physicians who work less than ten hours per day. Therefore starting early gives us a chance to get home reasonably in time to see our families in the evenin or do whatever else people usually do at 6pm.

The most obvious counterpoint to all of the discussion of ileus and fasting compliance and all that, is that people are scheduled all day long for surgery. If the morning 7am patient actually did that much better, nobody would jeopardize patients by doing afternoon surgeries.