There really arnt any rules about having your car running or not. Next time try parking next to a group that obviously plans to sit outside of their car. I've personally never heard a car running loud enough to be heard over my car radio in the first place however.
You do know what happens to a car battery if the radio is left on with no engine for 5 hours right? It's a shame people didn't want to drain their batteries and get stuck there just so you didn't have to hear a miniscule amount of engine noise, or don't know how to turn up your own radio to compensate...
There are no rules for your car to run or not or if you want to sit inside or outside your car it's all your decision
Not a good deal.
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