John: The PPE requirements at the factory I am most familiar with is the use of eye and hearing protection. While not that uncomfortable to wear, it is a common complaint from new staff. New staff are the most likely to violate this policy. Safety staff try to minimize the complaint by buying quality PPE, ear plugs that are comfortable as well as safety glasses that fit well and are comfortable to the wearer.
As a basic requirement for all employees, there are not a lot of innovative efforts to encorage their use, beyond writing them up and using the disiplinary process. This is such a basic requirment the use of efforts beyond that would be laughed at.