In the 25+ years I've been riding, I've taken lessons at four barns. Of the four, only one dragged the (single, outdoor) arena weekly. Another did it two or three times a month, and watered their indoor the same. The place I took lessons at as a kid/teenager dragged the outside ring maybe once a year? I don't remember ever seeing their indoor dragged. Watered a few times, yeah, because people were coughing so badly.