Quote Originally Posted by Nixxe View Post
https://store.steampowered.com/subscriber_agreement/

I actually don't see where this is included in their subscriber agreement without substantial creativity in interpreting them.
To make use of the Content and Services, you must have a Steam Account and you may be required to be running the Steam client and maintaining a connection to the Internet.
The Steam client software and any other software, content, and updates you download or access via Steam, including but not limited to Valve or third-party video games and in-game content, and any virtual items you trade, sell or purchase in a Steam Subscription Marketplace are referred to in this Agreement as “Content and Services”
As far as I can see, the quoted part has been present on the agreement since the start of Steam. So, it has been a thing always and people agreed to it.