AH, but if something happens, the gym can be held liable. I just read an article about that happening. The gym did not background check a custodian, and then he molested a young girl (lots of extenuating circumstances). The gym was found liable for not checking, and had to pay, eventually declaring bankruptcy. That gym now background checks everyone who works there. Smart practice....
I agree that background checks on all employees is a smart practice, and my current gym does. Unfortunately, due to a few moves over the years, I have worked at several other gyms so I know that background checks on all employees is not always a thing.