My objection to it comes in several forms:
1. Even if you install HL2 from CD/DVD, they still make you do a long validation before the game will install.
2. You have to continuously re-validate the game in order to play it. Even if you're not playing online. You also have to run Steam - basically an online service - in order to play, even if it's just single player.
3. In my experience, running steam generates a great deal of upstream traffic... even if it's just a single player, local game.
4. If something happens to steam, you are pretty much locked out of all your steam-related games and functions.
5. Steam wants to run all the time, which puts it in the same category of crapware as itunes.
6. I have no interest in most of the "benefits" steam supposedly offers. I don't play FPS games online. I don't care about all the crappy titles that can be distributed through that system, and I don't want to use it to communicate with other players. I wanted to play the sequel to what I found to be an engrossing single-player game. I couldn't tolerate what I paid for, and as a result, I've never even seen more than the first tiny bit of HalfLife 2.