I think it's largely dependent on what kind of civilian traffic goes on in a particular area; it's probably a common experience near the major metro areas.

For example, for alot of people far to the northwest of Chicago the largest amount of driving they are going to be doing is along the tollways/interstates going between the various suburbs and the city with their destination probably very close to an exit. There's just straight up less of a chance of running into a cop than if you were using regular streets/roads. With the volume of traffic on highways you have to be acting like a COLOSSAL dumbass to get picked out of that crowd, there's less police per sq. mile watching it, and whatever law your breaking has to be worth disrupting all that traffic and that's a fraught situation in itself. You may see cops parked on the median with their speed guns out but they're not checking your stickers or stopping people for having expired plates, they're looking for the guy going 120+ on the shoulder or overloaded trucks.

E) Thanks @stalinsmawaifu for bringing up "add-on" charges, could have saved myself some keystrokes if I remembered the term.

If most of the traffic is on regular streets with slower residential or commercial areas those police have literally nothing better to do than cruise around looking for something like this to pounce on.