Hmm..looking more into detail at tracks in real life, I've noticed that GT5's atmosphere is quite...dead. There's little to no fans.
For things like time trial and Sunday Cups, this is okay, but SUPER GT, NASCAR, F1, and Touring Car events should have a packed, fun, and exciting atmosphere: fans occupying the stands, flags in the grandstands (on some courses), the pit crew having their preparations and waiting patiently (not like in GT5), having more audience where they are allowed to, and a commentator in the ambience.
All this can make the game much more immersive, but it HAS to be done right. For instance, we can't have a sell out crowd at an FF challenge, a more of a vacant type is necessary at a smaller event. Also, please, please, PLEASE work on the crowd models. The crowd looks like they were made out of cardboard, then colored with a terrible printer. Make them nice enough to make the experience as good as possible.
End of wishful thinking.