I was going to say, "no one" is a bit too far. I read a lot of stuff. EUOL's last two manuscripts, for example, entirely on screen. And those are quite long
I should add something more relevant. I have two more thoughts.
The first is prompted by Stacer. Editors have a huge role in the production of a book. Most writers would be much, much worse without someone reviewing their materials. Whereas cartoonists have only censors, which don't apply on the web. There's something to that. A middle man is needed, because someone has to be paid for that except with the small portion of writers that can also self-edit effectively. It puts a cramp on the tranferance of the business plan idea.
The other is this: print comics are becoming more like web comics. You see a loosening of the former restrictions on content and ideas. Today, Get Fuzzy made D&D jokes. How many times have you seen that in print? Only in Foxtrot I'd wager, and that kid's supposed to be scary nerd, whereas Rob in GF is just this guy, a grown man who talks to his cat and dog and plays video games and D&D. Ok. Maybe he's scary too. But we're seeing much more humor that gets away from convention. Racial topics are much more open in print. Gender topics are becoming more serious. The humor is getting more off-beat.
I still think the average web comic, though bad, is better than the average print comic, but I think it's improving and even finding success with niche groups. On the Fastrack, for example, appeals heavily to computer hardware/programming familiar readers. Comics are having to change with the times. Cathy a comic about a pathetic single girl (the comic itself being pathetic too, but that's beside the point) has realized that something needs to happen to. It can't rely on single jokes forever. For decades it's been running comics about losing weight and man-hunting. The last few months have been about throwing together a wedding. And it looks like this week, she'll actually be married, which changes the dynamic entirely. She'll still be able to do fat jokes, but other concerns will come in and previous topics will have to be thrown out.
What does that have to do with publishing on the web? I think, and it's just a theory, I don't have a comprehensive set of evidence to back it up, but I do think that it's the advent of webcomics that are changing things. Non Sequitor, which was original at first but grew more and more tired as it went, getting old much faster than most comics, has had to start lampooning web comics for material. People have a different source of cheap or free comics. The newspaper has to improve it's material to meet the demand of the alternative and can't rely on it's old schlock standards like it did once. This means, at the very least, that web comics are having a major influence on the evolution of the art form. They're better at entertaining the new audience than print is (speaking in generalities only). Surely that means that money can be made there.