Plenty of people don't play through Origin. Some of us, myself included, have Steam installs, and we can launch the game without actually opening Steam either. Many people have all their packs on disc and a base game disc that was manufactured prior to 2012; these don't require Origin to manage the install process. In either case, Origin doesn't even need to be installed on the computer for Sims 3 to work. There's also no requirement for an internet connection.
Sims 3 also predates Origin by two full years.
Not that it matters, but Origin can and should run fine with no internet connection. It's supposed to default to offline mode, and while it won't load your game library, an installed game can still be launched from its .exe or desktop shortcut.
The Sims 3 Store doesn't require Origin either, just an EA/Origin account to use for buying and downloading content.
