What Good is a Law That's Not Enforced?

In yesterday's Tampa Tribune, a Letter to the Editor from David Johnston caught my attention. Johnston had relatives in town for the Superbowl. They stayed in downtown Tampa, but their stay was adversely affected, if not ruined, by the noise of loud car stereos, which kept them awake at night. Unable to change hotels, and needing to sleep, by Saturday night, they had had enough and moved in with Johnston.
He points out that they would not give the city of Tampa a B+. In fact, they likely will never return to our fair city.
Johnston pointed out that there are laws against this excess noise, but they aren't enforced. I'd have to agree; of course, some will say that since it was Superbowl weekend, and the partying went on quite late, but, I hear these earth shaking, blaring stereos every day.
You know what I'm talking about. You pull up to a light, and one of the cars, sometimes a couple of lanes over, is blaring some music - no, not music, noise - which often even includes obscenities.
I want to do something when this happens. I dream of making a citizen's arrest, but, of course, I would never approach the perpetrator, lest I be attacked and become the victim of stereo induced road rage. So, I suffer until the light changes.
I've tried this strategy once: I turned my radio up very loud - it was on a classical station - to try to overpower the other stereo, but, having a standard setup in my car, I knew I would blow out  my speakers before getting loud enough to be heard by the occupants of the offending vehicle.
Anyway, to David Johnston, I hear you, and I agree. There is a law, but I wonder if it ever gets enforced by the City of Tampa Police Department or the Hillsborough County Sheriff's Department.
It's kind of like the litter laws, and the laws restricting people from collecting money or selling things at intersections. They are on the books, and they are certainly taken seriously and enforced in other cities, but they are not enforced in Tampa.
We've got a lot to be proud of here, but we've also got a lot of things that need fixing. This is one of them.
What's the point of a law that is not enforced?