its true that you cant get true realism from any racing game, due to limitations of computers, 2d graphics (even if its 3d graphics, its still on a 2d screen 19" wide), sound coming from just a few speakers, and more...
if the original poster had given reasons, im sure this thread would have been a bit better. ill try and speak for him in wht i think are the unrealistic / arcadey things about LFS... of which we all know and have an answer for. ie the sim is still under development.
1) the damage and pinging of cars off of barriers.
2) the graphics lacking some details such as dirt.
3) weather effects are lacking.
4) the way public servers are short races, not taken too seriously, and are a pick up and play style.
well thats all i can think of that the OP would of meant with his post. and we could of given good reasons for why they are like that.