....to make this overly and horribly complex.
Amusing.
Not only do we have 3 or 4 different versions of the game, we've got this nebulous content delivery program called Steam which no one quite seems to know 100% how it's going to work as far as patches, content, and how it's actually connected to gameplay like single player, or what it all means to someone who just walks into a store and buys the singleplayer game, as opposed to someone who buys the whole thing online over Steam.
You get the feeling they said "Let's make it so people can buy Half Life 2 over the internet and download it when they buy it!" which sounds like a great idea, and then stuff kept getting added until it turned into a huge pile of yuck.