Ask Valve...

Why, they're going to release their next Half Life as a Linux exclusive? Or even any lesser franchises?

They've released a good bit on linux thus far as a hedge against the demise of windows as a gaming platform. Go do your own reading on the topic.

We were talking about exclusives, not hedges.

You asked the question: "Only, what would a game company care about Linux adoption?" Regardless of the content of your parent's context, you were specifically asking about why a game company cares about Linux. I provide information, you say it's irrelevant unless they're developing solely for Linux. How silly.

Let's just say that everyone is entitled to have a different opinion about what is sillier, ignoring the context of a question or deeming irrelevant an answer that is out of that context. Cheers!