In my line of work, there is no such thing as a weekend or "working hours". People that are retired are also in a similar situation where technically there is no difference between a weekday and weekend.

The problem is that others have decided that Saturday and Sunday are days of rest. The genesis of this being religion. So, whether you work or not, Saturdays and Sundays are significantly quieter. In my case, they are much more peaceful and productive. Come Monday, other people's bullshit (especially the one left unattended for two days) floods my inbox and blows up my phone.

TL;DR: Mondays suck anyway, thanks to religion. (/s...but just a little)