Why does Gordon never talk? Because
Gabe Newell is a
brilliant game designer.
Newell's reasoning, in his own words:
"The character of Gordon Freeman was left as transparent as possible to the player. There's no voiceover, no third-person camera or mirrors. We tried never to pull the player out of the experience through cut-scenes, voiceovers, even Easter eggs or other obviously authorial devices. We made the other characters in the game sympathetic and helpful, and then we did horrible things to them to try to get the player to feel both the loss and the sense that the world was actually dangerous. We left a lot of ambiguity in the story to allow the player to write the story however he wanted to, from what he was experiencing."
(quote from the book Game Design: Secrets of the Sages)
In contrast, I recently played a similar game called Red Faction. While the game starts off using techniques similar to Half-Life, they simply cannot resist the temptation to use cutscenes and suddenly my character "Parker" isn't me any more, he's this wiseass with a gun who wants to kill everybody. It threw me completely out of the game.
Gabe has apparently read chapter two of Understanding Comics, or at least came to the same conclusions independently of Scott McCloud.