Very few "WebGL" sites do any 3D. Mostly, they're just doing pans, zooms, canned 2D animations, and layers. I've been looking at galleries of WebGL sites. Other than demos, very few do anything you couldn't do in Flash.
3D in the browser has been here before, in VRML 97, Web3D, and Shockwave Flash. It's never caught on. The technology is great, but nobody cares.
There's now Web3D in the browser using WebGL.[1] (Web3D is just VRML 97 with XML syntax.) Nobody uses this.