A force must be acting on the ball. The force that slows down the ball is friction. Friction is a force that occurs when one object rubs against another. The ball rubbing on the floor creates friction. Different materials produce different amounts of friction.
Rough materials rub best.
They produce a lot of friction. Most smooth materials do not rub well. They produce less friction. Other materials, like rubber, are smooth but still produce a lot of friction. When you ride a bike, friction against the tires slows the bike down even if you are riding on a smooth sidewalk.