...There's an offline mode for Steam. I can play all of my games offline a lot of times...b/c my internet kinda sucks. I understand your concern but Steam doesn't force you to go online to play your games...
And how did you actually test this? Unless you physically disconnected your computer from the Internet or used a decent third-party firewall to block network access for steam.exe, then you're not actually offline - Steam can (and will) still make online checks, though less frequently, as noted in
Valve's Offline FAQ and confirmed by
multiple reports from other Steam users.