You are either naive or new to this planet. If you tell industry that this or that thing is voluntary, it will definitely not happen. There must be thousands of examples out there. “Voluntary” regulation never worked on this planet.

If you want industry to do something, there is the stupid way of bribing them into it, and the smart way of simply forcing them to comply. If you do the latter, they will still squirm, complain, and demand money (loads of money!) to follow the law. If you forgot to define fines for non-compliance or made them too small, they won’t follow the law, either, of course, so the fines have to be painful enough so they can’t just file them away as “costs of doing business”.