No answer on why some, but I think you can condition your body to it to not get sick. Good thing is that they have some over the counter meds that work great. I get motion sickness on the track--even driving! Over a recent track weekend I felt like crap on the first day, on the second day, I took one of those chewable pills, and the motion didn't bother me at all.
Of course if I would just learn to drive smoother, I probably wouldn't have a problem at all
