People do get kidnapped at traffic lights. Here's an incident of it happening in Florida a few months ago.
The ability to arbitrarily stop vehicles would be very useful for this kind of crime because it could be done in less crowded areas. And criminals could more readily select for expensive vehicles, young women or whatever else they're wanting.
But the comparison we are making is different - do people create a fake traffic light, because that is really easy; and I have never heard of it happening.
Ofcourse there are places where vehicles have to stop naturally, you can’t avoid that.
A convincing set of fake traffic lights requires a meaningful amount of time and equipment, as well as a plausible set of crossroads or roadworks.
To steel man your position though, a fake police costume would probably be just as effective at stopping vehicles arbitrarily. And despite being cheap it's a relatively rare occurrence.
Ofcourse there are places where vehicles have to stop naturally, you can’t avoid that.