My idea was more like "one-click play" for inexperienced users. For example from the browser when you click on a link with a certain protocol the browser lets you choose an app and I assume Steam will be the one you'd select to open. From there, the game could be launched directly. Instead, with ...

TL;DR
Support connecting to a multiplayer game with a Steam protocol URL


What?
Steam adds support for a steam:// URL with its own protocol on Windows machines when it's installed. It allows to do multiple things, one of which is directly connecting to a multiplayer game server. For example ...