What makes people think they can park in a "truck load only" zone and *not* get a ticket? I work in a store on Market Street with a truck zone just outside. The sign is clear and unmistakable: "DON'T PARK HERE between these hours, unless you're a truck making a delivery or pick-up."
Yet, every day I see dozens of people park there and "just run in" to a restaurant or perhaps to use an ATM, etc. Often, they're only in that spot for less than ten minutes, though just as often they're out there for well over the 30 minutes the sign allows (that 30 minutes is for trucks, mind you).
I take great pleasure in seeing the small fraction of people who get tickets for their behavior, and especially those who try to talk their way out of it. I can tell you this much: You park your car in a truck zone to go get lunch (or really, at all), the three parking cops I've seen will NOT be cutting you a break, no matter your excuse.