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.