Don't get us wrong. We love all those other sites and use them every day. The only thing is, airlines these days sell many of their best fares on their own Web sites, with special site-only sales, promo code fares, and other deals.
Airlines don't pay folks like us (or folks like Kayak) to refer you, our valued readers and users, to these special fares. So most airfare sites tend not to list these fares in their searches. Gotta pay for all those programmers and venture capitalists, after all. But we do tell you about what we call "airline-site-only" fares, including deals on Southwest, even though we don't get paid for doing so, because Airfarewatchdog.com was founded by a travel journalist (me) specializing in consumer travel issues (I was an English major, not an MBA student, although many of my best friends do have MBAs). So if you're new to our site, please take a look around and sign up for our free alerts.
One thing: those other sites do cover more routes than we do, and their fare alert systems offer some bells and whistles that we don't, so do give them a look, too!