You're shifting the goal posts. Nobody was claiming that ABI stability would lead to an increase in products, I was replying to you claiming ABI instability as a significant obstacle. As for the number of binary-distributed desktop products for Linux not having grown lately, I think you're completely wrong on that: See the Humble Bundle games.

And the userbase being so much smaller is, again, why Steam for Linux is such a big deal: It's an extension to a platform publishers are already familiar with, which makes it easier than ever for them to add the platform.

On top of that, Steam is more than just a distribution platform, it's also an SDK for things like multiplayer lobbies, meta-game systems like achievements and savegame sync. Dozens of titles are using that SDK now, and getting it ported to Linux maikes Steam for Linux also an important middleware port.