I'm not sure how this perception continues to be so common, but you do NOT have to be online to play your Steam games. I live in the woods and lose my cable connection a couple times a month (forest + wind = downed lines).
Unless the game's publisher has some kind of other DRM implemented, you can load up Steam and play just fine without a connection.
Also, not all games you buy on Steam require the Steam client to be loaded, that again depends on the implementation of the publisher/developer. Many games can be launched with a shortcut directly to the EXE just like they were installed from anywhere else, although this is admittedly more hit and miss and difficult to determine before buying short of just asking other users on the forum to verify.