Live chess Ratings is volatile to Periods of day /week you play

I have notice some time ago that there are more strong Live chess players at the week days from monday to friday and the daily western time zone.

In practice this means that when I play in saturdays or at late night the general level of play is very inferior almost 100 rating points.

When i play against a 1500 player ate weekend He can be a very weak player.

Now I want to know why this is 

- is it because less or no "pros" come to play at thes period of time?

- is it because less CHEATY /Engine / Bot players come to play in these periods of time?

- or more amateur players in weekends?

People get tired (& drunk).  Their ratings suffer if they show up on site in less than optimal condition.

sftac