Web Comics and Mondays

I don't buy into that "Monday Blues" thing. At all. Weekends are every bit as busy as week days, so the shift from Sunday to Monday isn't that big a deal.

Given that, look at the posting schedules for web comics. Here, I've prepared a handy chart of the web comics I read regularly...
See a pattern? Every web comic posts on Mondays! Why is that? I understand why the dailies (Sheldon) and week-dailies (PVP, Evil, Starslip) would all post on Monday, but why the others?

Seems like a traffic opportunity to me: someone oughta start posting a weekly on Tuesdays.

(BTW, I couldn't find a good way to add links to each line in the table, so here they are...

• Sheldon
  
• PVP
  
• Penny Arcade
  
• XKCD
  
• Imy
  
• Legend of Bill
  
• Evil Inc.
  
• Starslip Crisis