The Washington, DC show - actually held in Virginia, near Dulles Airport - has a lot more dealers than the OP experienced in Vancouver. It's an opportunity to see a lot of RVs in a few hours. Maybe you can do most of your research online, but some like to look, even if not interested in buying that model or class, or already bought and aren't in the market at the moment. It's cheap entertainment, and the Virginia State Parks give out a brochure with a half-price camping coupon, which pretty much recoups the admission fee for the show.