I commented it elsewhere but it can be tough to balance general laws like that. E.g. right now, if an employer is aware people wear face masks so they can chat on the phone while they drive then the current set of laws allows a lot of liability to be placed on the employer when such accidents occur due to not taking safety seriously enough. Putting a general rule that an employer can't do this sort of thing then runs the risk of employers saying all sorts of things were for the workplace environment compliance, not safety negligence on their part. Putting specific rule exceptions instead becomes daunting to define, keep updated, and understand (for employees as much as employers).
I'm not saying some of this kind of thing can't be better served by some different laws, just it's probably not as easy to solve with a "quick" law or these other approaches as it might seem.