What is it.........

I’m going to say it’s because the car radio runs off battery power and doesn’t have the harmonic distortion of AC powered systems.

Also another complete guess is that perhaps when our brain hears a low bandwidth signal it isn’t expecting anything to do with real sound, and fills in what’s missing.

When you hear a full bandwidth signal with actual dynamics, maybe the brain is expecting some thing more literal, instead of the mere represenation of music.  

in the same way, you can watch low quality comedy YouTube image and still laugh as hard as watching it in the theater, but it doesn’t have the immersive quality.

Also think of a voice over a squawky phone signal.  You will get the content of what someone is saying, but you might miss small cues like a sigh, that indicate additional meaning. 

The car is isolated from seismic type vibration by springs and gas pistons and there are no crossovers in speakers or room issues.

Sorry, I cannot relate to this post. I cannot think of a single instance where any music played on an inferior system, much less a radio, was more moving, compelling, soulful, etc. than on my finest system.

Imo, emotion or soul of the song is not conveyed well on poor audio systems. YMMV

If  you had ever heard ANYTHING played through Richard Clark's award winning Cadillac or Buick Grand National audio systems back in the day, your mind would be completely changed about what's possible in a car environment.

Oz

Further, I realize that there are some good car systems, so ozzy, your point is well taken. Yes, sound quality can be terrific in a car. I choose to neglect that for several reasons; I have a very short commute and could even walk to the office if I wish, I am disgusted by engine noise (especially with an 8 speed and engine revving more), wind noise, road noise. I strongly prefer a perfect environment to listen, which is why I built a custom room. Given those conditions  I choose to put nothing additional into car audio. I can see why others with longer commute, etc. would wish to. 

I remember as a teen listening to Toto, et. al. and immensely enjoying it as played on a boom box. Now, I get to enjoy and appreciate the performance much more. 

Bottom line is, I have always been very sensitive to the quality of the music, and the higher the quality, the more I connect with it. That's one reason I am a System Builder, beyond being a music lover. 

Could you be any more argumentative?