Why is section 4307 of the Pennsylvania vehicle code a Law?

So not to long ago i was ticketed in Pennsylvania for having an "illegal illuminated display sign" aka section 4307!!! Now im wasn't sure of the laws before regarding this before but i didn't think it was illegal since mostly the only lights i thought where illegal on a car were cops lights "red and blue". Now of course i fought the ticket, but when i did i was quickly found guilty within 10 minutes of my court session. When the case was finish i then asked the Judge, why is this illegal, and with a confused look on his face, he said he didn't know, he just was following the book!!! I then decided to appeal the ticket more to a higher court on which later the officer who issued the ticket threw it out. Anyway my question is why are LED signs illegal in cars? yea i can be a distraction, but ok, anything a distraction, i mean come on there on buses and there much brighter so don't you thing they would be more of hazard? Honestly is this just a way to make money because if they sell it at retailers for your car, why does the state allow them to sell the item for your vehicle?