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.

What U.S. courts will look for is an industry standard for safety, even if implicit, and then see if you are meeting or exceeding that standard.

In the U.S., for climbing gyms, part of the standard is a belay test. In the article, Mayfield talks about trying to get the industry self-regulating before the government steps in. This is basically how that works: industry founders or leaders establish some procedures for safety, prove them out over time, then insurance companies implicitly adopt them and everyone else follows.

> What does that have to do with US gyms requiring belay tests, which is a bunch of steps that doesn't involve "extensive warning in writing".

It lowers insurance bills. If you don't let anyone climb without having done a belay test and putting that paper in a cabinet for 10+ years, then you can get cheaper insurance.

It's the same reason why some gun ranges won't let random people in without joining up and going through a safety intro thing - cheaper insurance.

Insurance.

Which requires due diligence.

Which means there is some guarantee that people belaying at the facility meet some basic standard of skill, so that people are not being dropped all the time and then turning around and suing the facility for negligent supervision/creating a dangerous environment.