I'm a little confused. I just booked (or nearly booked) a flight from ORD to EWR on May 30th on expedia.com and right before I booked, I got a message saying, "Although this itinerary doesn't qualify for ThankYou Points, you can still earn points if you add a hotel booking today or any time before you travel."

Why on Earth wouldn't my ticket qualify for thank you points? What are the rules for this?