It isn't. My state is looking into making the penalties stronger and people are generally favorable for that because they still see people driving every day with their face glued to their phone.
The only people against distracted driving penalties are people who are entitled and think they should be able to put others in danger for their minor convenience or libertarian assholes who think seatbelt laws are oppressive nanny stating.
Selective enforcement and high penalties is not a solution. Simply enforcing existing laws would be trivial and solve the issue. The only problem is people would not really want that, just like they would not want police to enforce speed limit laws.
The other way to think about this, how much of our phone use when driving is because of lack of public transit and the requirement to commute to work? There are different ways of addressing the same problem.
The only people against distracted driving penalties are people who are entitled and think they should be able to put others in danger for their minor convenience or libertarian assholes who think seatbelt laws are oppressive nanny stating.