It's worth it.   They place counters on roadways for cars.  Why not bikes?   It goes to demonstrating evidence that trails are being used for future planning purposes as well as budgeting for maintenance.    There are cities in Europe that are banning cars from central areas to eliminate congestion and promote cleaner air.   While there remains here a large proportion of population who have an innate need for Hemies surrounded by iron, there is a growing demographic that relies on bicycles for  personal transportation.   As with education, you don't  need to have children to benefit from tax dollars paying for it.