The problem is that the mids and high frequencies are at that high of a level, most car stereo's even though they are booming out 130+ dB's of bass, are only around 100-110 dB max on the mids and highs, which are what really damage hearing.
Also at a concert you are listening to that volume at a more constant duration over a longer time. In a car you generally turn it down once in awhile to converse with passengers, order at the drive through, make sure the cop doesn't pull you over etc.

 

Oh and that chart is probably C weighted or something as well.