I think you might be underselling how important things like the steam workshop and steam's multiplayer support are.
Games like Starbound or Don't Starve benefit a lot from the workshop.
While insert any party game gains a lot out of steam's multiplayer support and friend list.
Also, while I don't use Linux myself, Steam is one of the main reasons why Linux Gaming is a thing.
I wish I was this deluded. Life must be so simple when it can whatever you want it to be.