Earlier quoted context omitted.
Valve isn't beholden to any external shareholders, and Steam is as close to a money-printing machine a private company can have. Combine that with the fact that Gabe and company seem to have pretty decent values in line with their customers' interests, and you get nice outcomes like this.
And let's be realistic, this is going to sell an absolute crapload of HL2 to a whole new generation of gamers.
And that's ignoring the fact that HL2 is 90% off right now ($1) and they're giving away HL1 for free.
No. Valve just does whatever Valve wants. The most valuable thing they're getting out of this is probably goodwill.