Tennis balls are something that don't seem to last very long, and there's actually a reason for this. The main culprit is the air pressure inside the ball which starts to leak over time, leading to a decrease in bounce. The ball's surface also wears down with use, making it less aerodynamic. Furthermore, exposure to various weather conditions also affects its longevity. In short, while tennis balls are made for durability, they are not immune to the wear and tear of constant play and environmental factors.