There are several pieces of received wisdom about innovation that explain this. I'll look at a few of those and try to de-bunk the commonly held view.
1. You can't "manage" innovation. Really? Tell that to the major consumer goods manufacturers who crank out hundreds of new products each year. Do you think that happens by accident? If they can do it, why can't every firm become more process oriented around innovation?
2. People won't use innovation processes or tools. This one takes me back to the early CRM days. Every skeptic I met told me that sales people would never put their data into a system. 10 years later, everyone uses CRM - Salesforce.com has been a huge success. People will use tools that make them more productive and more successful.
3. There's no defined process for innovation. It seems to me that in general people dream up new ideas, and then write them down. The person who came up with the idea, or someone else, decides whether or not to pursue the idea. The idea is evaluated and people make decisions about putting that idea into a new product development process. There are logical, repeatable steps for innovation, and these can be written down and codified.
4. Too much management of innovation will stifle creativity. Actually, quite the opposite. Even today, most managers tell me their problem is too many ideas and no consistent way to capture and evaluate the ideas they get. Creativity is interesting, but putting ideas into action is valuable.
There's a page full of objections and complaints about innovation and the challenges that a firm faces, but let's be honest - a lot of this received wisdom is simply fear of change. There's going to be some change involved in becoming more innovative, but let's not allow some unreasonable notions about how difficult it is put the brakes on what we do. If we fail at innovation, let's fail for a real reason rather than some simple objection such as these that can be easily unmasked.