1. You
can't start Steam in offline mode, you must start in
online mode and then switch over.
2. Steam is required to run the game.
3. Steam
is DRM - I'd argue a fairly intrusive one but it's marketed as a "service" (which it is).
4. Steam is an evil monopoly
5. Steam is not viewed in a negative light because of how widespread it is, if 10 years ago I told you you couldn't play your game unless you installed third party software and connected to the internet and updated your game you'd probably be more than a little angry. However nowadays with games like MW2 being exclusive to steam (who were then able to jack the price to 90USD) just about everyone has it and doesn't bat an eyelid at all the downsides - which have become "services".
Besides, it's up to the devs whether it's' sold on Steam, I hope not but it's not my choice