In fall 2006, the National Basketball Association (NBA) started using basketballs made with synthetic, or manmade, material instead of leather. They made the switch because they wanted every basketball they use to fell and bounce(弹起) the same.
　　However, some players complained right away that the new balls bounced differently and were actually harder to control than the leather ones. Dallas Mavericks owner Mark Cuban asked for help from the Department of physics at the University of Texas, The scientists investigated friction that affects the ability of a player to hold onto a ball. “The greater the friction, the better it will stick to his hand,” explains Horwitz, one of the physicists who worked on the project.
　　Tests on both wet and dry ball showed that while the plastic ball was easier to grip when dry, it had less friction and became much harder to hold onto when wet. That’s because sweating stays on the surface of the synthetic ball but get absorbed into the leather balls—an important detail for sweaty athletes
　　In January, the NBA went back to using the traditional leather balls. They aren’t perfect, but for now, that’s just the way the ball bounces.The NBA started using synthetic basketballs instead of leather ones because____.（　　）