Maybe it's because surgeons on average tend to put off more difficult surgeries to a later day in the week. They don't want to come into the operating theater a

Maybe it's because surgeons on average tend to put off more difficult surgeries to a later day in the week. They don't want to come into the operating theater after a weekend of hard drinking and have to do a complex brain operation on Monday morning. So they will organize their schedule so that they only do routine low-risk operations on Mondays.