Is there a particular rationale for this rule?
You're much more likely to see such ordinances in states that don't require front license plates. https://blog.appwinit.com/states-that-require-a-front-licens...
Note that this is for "for city administered public parking within the city" and doesn't apply to private / commercial lots (which may have their own parking restrictions).
Is there a particular rationale for this rule?