Many parents cannot afford to pay for sports outside what is offered at their school. Many kids may have interests outside of what is offered - martial arts, rock climbing, gymnastics, etc.
If we are to make America healthy again, our kids need to be active. We are letting the future generation get addicted to devices and video games early on. Parents cannot afford to keep them active all year, every year, as they progress; the purchase of a tablet device is a much cheaper alternative.
Subsidize what we want more of - healthy kids and young adults.