I wouldn't say no one uses a solution like this. Unity has a webplayer and it is becoming widely circulated. You only have to install the plugin once(same with java), after that, all the game content is streamed to your computer while you never leave the browser. It locally stores some of this content if you wish so you don't have to keep re-downloading the same game again. This works quite well, so I hope 3DGS does this one day.