Prestige Car Wash Soft Touch Bay 

It's so any excess water in it doesn't drip onto the car.

This system uses spot-free rinse and an onboard dryer cycle. Even if spot-free wasn't displayed on the wash process sign, it would've likely been included with all of the wash packages since not having spot-free water can sometimes form spots on a car if the dryers aren't affective at blowing all the water off.