Perhaps because Northwest Airlines offers a more complete relationship with KLM, a limited America West partnership, a limited Malaysia partnership, better promotions, a real Elite line, the ability to redeem coach awards on Midwest Express (and fly in a business class-type product), enjoy a token Million Miler program, full Elite bonus on minimum mile flights, complimentary upgrades on coach award tickets (in markets where one would normally receive EUA upgrades), and to receive discounts on a better lounge program (WorldClubs).

That being said, Continental isn't that much below WorldPerks-- just a notch or two. And a few short years ago, Continental was a far better program.