I think being able to download and update games is still enticing enough for Publishers.
If Steam were in a vacuum, sure. But Origin and UPlay are both things which do the basic download/update (and, hell, I think you can gift games in both clients, too!).
Steamworks is a lot of things
Steamworks tools
Edit your product's Steamworks metadata
Add and edit Achievements
Create and edit your product's presence in the Steam store and community
Author gameplay stats definitions and descriptions
Steam Community Integration
Game Hubs A collection of the most popular official and user generated content for your game including Screenshots, Videos, Game Guides, Artwork, Discussions, Workshop Items, News Posts, and Official Announcements
Official Game Groups - Communicate directly with users by using your dedicated game group
Steam Workshop - Allow users to easily share and download custom content for their game or software
That's a lot that is useful, but also, not so much that charging is a foolproof idea.