Hey, it beats fighting actual crime.
Meanwhile, enforcement is worried about offending child molesters, murderers, gang members, legal gun owners.... the list goes on and on.
Running people off the road and handing them a bill for not wearing a seatbelt IS the actual crime. Armed robbery, to be sure.
Troopers don't "fight crime" as you imagine the local PD does. Their mandate is to make the highways safer and reduce collision deaths.
They believe a large benefit exists to enforcing the seatbelt laws. It is their belief that doing "stings" or "emphasis" patrols like this will increase seatbelt usage and lower highway deaths.
WA has or nearly has the highest seatbelt usage rate in the nation so these emphasis patrols, it could be argued, do not accomplish the above goals.
You bet!
They sure weren't interested in finding my car when it was stolen.
That sort of thing doesn't bring in the money and kudos from the traffic judges like busting those dangerous seat-belt violators does.