This is actually one of the major selling points for Cloud Gaming. Although it still has a lot of issues to be adressed before getting into the mainstream, this is exactly what it promises. Just sending your friends an invite link and get them to sign up is a much more pleasant experience than downloading 100+GBs of game files before being able to join the session.
I also enjoy seing browser implementations of popular games. My favorite recent example is the classic version of Minecraft running in the browser [0]. The browser is obviously a much more restrictive environment than a native app, but I can still imagine plenty of useful examples for performant 3D graphics in a browser. After all, Games are often just used as a showcase for the capabilities of new Apis and performance improvements.
