Without question this is the most common question we're asked, often preceded by the nice compliment, "Your stuff is as good or better than the strips in my newspaper." And it's a good question, for which I don't have a particularly short answer. Here's the long one.
There are fewer newspapers every year, the ones that remain have shrinking circulation, and the space they allocate for comic strips continues to shrink. Readership skews towards the older part of the population, and they tend to complain when their favorite strips are taken away, even if they aren't really any good any more. So the actual opportunity for new comic strips is quite small, akin to a write getting her screenplay made into a major Hollywood motion picture.
It's made harder by the number of middlemen. A syndicate looks for material by second-guessing what a newspaper editor is second-guessing their readers would want. If you're second-guessing what a syndicate would want you've totally lost it.
And if you do get syndicated, those middlemen act as several layers of editing and/or censorship. Editing can be very valuable - Gene and I write the strip primarily by editing each other's work - but it can also get in the way. Would an editor have allowed this week's sequence, which touched on the recent debate over a YALSA award given to Orson Scott Card, who has written negatively about homosexuality? Maybe, maybe not, but I'm sure glad we didn't have to convince anyone other than each other.
And syndication isn't a free ride. When we sell books or merchandise we don't have to split the proceeds with anyone, and we like it that way. And it can be even more limiting, because we'd probably have to put our comic on their website, not ours, which would significantly reduce our connection with our readers, not to mention our opportunity to make money via sponsorships and promoting our goods.
But there's a downside to our control-freak existance. And that is that webcomics aren't as discoverable (or let's say, differently discoverable). You probably discovered Unshelved because a friend or coworker recommended it, or you followed a link from a listserv or blog. But many others followed that link and weren't compelled to return by what they saw. I am a little sad that there aren't hundreds of thousands of people who read our strip in their paper day after day, slowly gaining a taste for our style of humor. Nor are there folks who start reading our strip because they picked up a paper at the barber and start reading it. It's a lost opportunity. I'm not sure how much, but I do wish we had a way to reach a broad and highly diverse audience day after day.
Bottom line: all in all we like being on the web, and it's been years since we seriously discussed the possibility of newspaper syndication. But we are almost completely dependent on our readers to expand our audience. Thanks to everyone who has told a friend or coworker, or blogged about us, or posted to a listserv, or skywritten "unshelved.com" above the Superbowl. Well, it doesn't hurt to ask.