Believe me, you're not the only one pushing for a more frequent update schedule. And the person who's agitating loudest for it is ME. I would love to be able to stick to a daily update sched, or even M-F; it would make it easier to tell stories in a reasonable amount of time and it would keep everyone's interest level high. It hasn't escaped my notice that nearly all of my own favorite webcomics update at least five times a week.
But... unlike many web cartoonists, I have a lot of "real-world" obligations. I have a wife and two kids who, understandably, are jealously protective of their claim on my time; I also have a full-time job and a variety of household responsibilities. I decided when I was first starting this comic that it would be better for me to just do MWF and actually update on time than to try M-F and wind up not being able to keep it up.
That said, I really do want to move to M-F, and I'm a lot faster at doing a comic now than I was when I started. I hope to do that sometime in the next six months or so - we'll see!