You don't have to be always online with Steam. In fact, you can be offline all the time after registration if you want. Why do people keep hinting at that? About Steam adding to your game. Assuming they didn't use Steamworks (or another similar service), they'd have to develop all these things themselves. Instead they now get to focus on other aspects of the game, like AI, code optimizations, graphics, balancing, and so on. If that's not added value to your game, I don't know what is.