Because they have evidence "in writing" that everyone at the gym had to pass a test that proves they know how to properly and securely belay a climber. In the e

Because they have evidence "in writing" that everyone at the gym had to pass a test that proves they know how to properly and securely belay a climber. In the event that there is an accident, the liability falls completely on the belayer and/or the climber and not the gym itself for allowing someone to participate in something that is "obviously dangerous" without demonstrating they have the ability to do it properly.