One of my close friends is a state trooper. He says that lately the higher-ups have ordained that the best way to protect the public is "policing by the numbers".
As I understand the concept, some egghead did some research and concluded that the optimum way to police a community is to divide police man-hours up into X% traffic enforcement, Y% patrolling high crime areas, Z% community relations, etc. And each of thiose categories is further subdivided by percentage: while you're performing traffic enforcement, you goal should be to come up with A% speeding violations, B% drunk driving, C% seatbelt violations, and on and on.
My friend hates it. It removes any ability he has to use his judgment and experience to do the best job he can. Instead, he's been reduced to a bureaucrat filling up his percentages. Even if he knows crime is likely taking place in another part of town, or that there are people who need his help right now, he can't do anything. If he's scheduled to give out 10 seatbelt tickets per hour right now, that's all he's allowed to do.
So it sounds like the seatbelt-ticket-instead-of-speeding-ticket thing feeds right into this. The cops need to make their numbers on the seatbelt violations, so they go where they know it'll be easy to convince drivers to accept a seat belt ticket, even if the driver was in fact wearing a seatbelt.
