I wonder what a user is worth to Steam?

They didn’t have to acquire the user themselves and now they have more eyeballs on their service. How many of these users buy a few things later and make waiving the fee worth it?

Steams not doing this out of the goodness of their hearts.

nobody claimed otherwise, only that its trivial to sidestep the 30% fee, even if you wish to remain distributed by steam.

Right, they believe their store value is enough for them to compete with 0%.

Valve is definitely getting some kind of money out of the deal.

They are not

"Steam keys are meant to be a convenient tool for game developers to sell their game on other stores and at retail. Steam keys are free and can be activated by customers on Steam to grant a license to a product."

https://partner.steamgames.com/doc/features/keys

I didn’t mean to say they are getting a direct cut as sibling commenters indicated, but Valve definitely is getting at least some kind of money indirectly out of them offering this.

I'm a developer who uses Steamworks. Keys are free for us to generate and sell at will. Valve reserve the right to say no, but from what I can tell, their only policy is to not take the piss (selling millions of keys), and not to charge more to customers who buy directly from Steam.