Traffic creates coordination problems that infrastructure doesn't always solve. Two lanes merging to one, both drivers with equal claim to the same space, neither wanting to yield first, the gap between cars too short to fit a third vehicle but wide enough that someone has to decide. Most of the time people navigate this through a combination of posted rules, eye contact, and whoever accelerates first. Occasionally — and there's footage of this, so it's documented — drivers in slow-moving or stopped traffic throw Rock Paper Scissors through their windows to decide.
The cases that have gotten press attention share a common structure: both drivers were already stopped or moving very slowly, they had already established eye contact and were clearly amused by the situation, and the throw was quick enough that it didn't create a new hazard by distracting them. The appeal is obvious. The mechanism is unambiguous, takes three seconds, and both parties accept the result with no negotiation required.
The practical limits are also obvious. A driver who is moving at speed, who has to take their hands off the wheel and look sideways, is adding risk that the merge situation doesn't require. The zipper merge — both lanes proceeding to the merge point and alternating one-for-one — is the actual traffic engineering solution for heavy congestion, and it works without any coordination between individual drivers at all. In most merge situations the game isn't necessary because the solution is built into the road design.
Where it actually makes sense is in the genuinely ambiguous situations: two cars arriving at an unmarked intersection at the same moment, a narrow construction zone where two cars face each other and one has to reverse, a parking lot standoff where both drivers want the same spot and there's no clear right-of-way. In these cases, Rock Paper Scissors is faster than waiting each other out, more fair than whoever honks first, and less confrontational than an argument. Traffic engineers didn't design for it. That doesn't mean it's wrong.