It is no secret that prolonged exposure to loud sound is highly damaging to our hearing. Listening to loud music is one of the common factors leading to degraded hearing ability and tinnitus, and is deeply unhealthy.
At the same time, such level of noise negatively impacts the quality of sound perception, which degrades the musical side of the musical performance.
In what seems to be the echoes of the so-called "loudness war", bands still stick to the idea that "the louder you blast it - the better". But it's not true. There are many other ways to energize the crowd without causing them sound damage, and I'd love to see more of those, instead of them trying to be the loudest ever.
I can definitely see where wearing earplugs while driving a car could be problematic, because you can roll the windows up, and I would expect that your ability to hear emergency vehicles would be hampered while wearing earplugs in a closed car.
On the other hand, hearing impaired people - including those who are wholly deaf - drive legally all the time, so I'm not entirely sure where earplugs would land.