Why was I asked this by the traffic cop?

Earlier this evening I was pulled over while returning home from a trip. The officer, in addition to asking to see my license, asked if there was a phone number I could be reached at in the event that they have any questions for me. I've gotten speeding tickets before, but no one was ever asked for my number. Why would the officer do that? And what questions could they possibly ask? I was driving with a valid license, my insurance is paid up, and my registration and inspection sticker are up to date. What else is there for them to inquire about? This incident occurred in Jefferson Parish, if I remember correctly, in Louisiana. Sorry, don't have the ticket right in front of me; it's still in the car. Don't know if it's relevant, but I just thought I'd mention it just in case.