Everything in auto sales is a game. The more information on you they have, the more they can "persuade" you to buy at numbers more favorable to them. They look at the status of your car. If it's clean, they think you're more serious to buy and might not have to negotiate as low. If doesn't look like you've made the effort to clean it out before getting rid of it, they might think you're just shopping.

If they know you're looking at other dealers, then yes, they might think they need to play harder. If they know you're looking at accessories for this new car, then they can think you're more ready to buy. Every bit of detail they can get, they will use.