
Why? Because innovation means revolution rather than evolution. Innovation comes with (too) large improvements on existing ideas or concepts. This is where the trouble is: revolution might result in consumers not buying it because it's too extreme.
An example of true innovation in fly rod design is ArcticSilver's idea to ditch the cork grip for an integrated plastic handle. Hmm... Their idea certainly makes sense but I doubt this idea will be a big success. It's just too extreme. There's very slight resemblance to Sage's Center Axis rod series. The idea is nice but the Center Axis rods wasn't a huge success either. Mainly because you're stuck with the reel that came along with the rod and the price was pretty stiff too.

Rod companies that comes on a level below the high end companies (Sage, Winston and Thomas and Thomas, etc.) are probably more willing to experiment with true innovations. Mainly because they don't have a big customer base as well as the financial effects of failure is smaller.
Echo is a low to mid range price rod manufacturer. And it's no surprise that they came out with a very innovative idea with their new Shadow 2 rod at the recent IFTD (International Fly Tackle Dealer) show. I like the idea behind the Shadow 2 and the price point is amazing!
Revolutionary innovation isn't always a failure. Apple released the revolutionary iPhone in 2007 and the phone industry changed completely. Same goes for the iPad.