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.
The least dangerous way of using a device while driving is to hold it in front of you in a way that doesn't block your forward field of few but also doesn't require you to look away as mounted devices do.
How about making it so cell phones limit most functionality when in a moving car going faster than some threshold, unless making an emergency call?
Perhaps with an exception that allows full functionality if the car and the phone support some way to precisely localize the phone within the car to being somewhere other than near the driver?
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.