I wonder the same thing. There are a handful of old jetways that can't get low enough...otherwise, the ERJ is designed to fit a standard jetway with no extension. I wonder since some stations serve CRJ's (which needs an adapter) and ERJ's with the same jetway so they don't bother removing the adapter when we come into town. You're right, it defeats the purpose of the ERJ's "Jetway door" entirely.