First off, Hayward is NOT, I repeat NOT, a suburb of San Francisco. Hayward is on the east side of San Francisco Bay, i.e. east of San Francisco. Contrary to what those in the pit, aka San Francisco, would like to believe and continue to delude themselves into believing, SF is NOT the center of the universe, nor are those who live in that special place.
The Bay area, however, is home to hundreds of thousands of Silicon Valley geeks/ types. (I work with them, am married to one, and have raised two...)
That said, what these signs illustrate and demonstrate is that no matter how pervasive the nanny state is, there is no cure for STUPID x 1000. I'm waiting for someone to run into one of these signs because they were distracted / amused by it...and, well, who know what happens next.
And, lastly, it is most important to remember that while Hayward isn't a suburb of SF, it is in California. THAT alone should tell you everything you need to know. California already has laws on the books prohibiting talking on, holding, or texting via phone while driving. That legislative boondoggle is about as effective as an open screen door on Noah's Ark!
BTW, I don't live in Hayward, just nearby the town.