While I do appreciate Valve's support of Linux, it's hardly altruism: it gives them some room to negotiate with/pressure Microsoft. (i.e. while it would be painful to push even a fraction of their users over to it, it is an option Valve has) Compare that to the situation app developers on mobile platforms find themselves in these days. So it's smart strategically even if it doesn't translate into big $$$ currently.

Maybe they're not breaking bank but for a company whose revenue is measured in billions, moving the needle by .1% is worth millions..

I know many Linux users who have abandoned competitors (GOG..) for Steam due Linux support.