This makes sense, from a political perspective. Cell phone usage while driving causes major harm, and while hands free devices don't significantly reduce that harm (https://www.fastcompany.com/91076805/cellphones-hands-free-d...) banning use of cell phones while driving is politically untenable, because constituents want to be able tu use cell phones while driving. Writing a law to ban the holding of a cell phones while driving, without banning their actual use, provides the appearance that politicians care about the constituency, without the inconvenience of regulations that actually impact safety.

From a statistical perspective, it's possible that it's worse than having no regulation at all, because people take more risks when using safety equipment (https://pmc.ncbi.nlm.nih.gov/articles/PMC4767144/), so ineffective safety equipment might increase risk taking, making a net negative effect.