I'm not sure the law is unenforceable, just not always actually enforced when it could be.

Umfortunately there are those who simply cannot resist using their phones no matter what situation they are in, I've seen people shooting a video to put on You Tube, pausing to check Facebook while they are actually shooting.

How about this woman who in the run up to hitting a cyclist, had made and received 44 texts during the previous few miles travelled.