Probably comes down to a $$ thing. I know the track I raced at in SoDak flipped back and forth a couple of times. They've been IHRA for a long time now though. I did note that the track does still use "K" rail and I believe the NHRA wanted them to have concrete walls the length of the track (like Vegas). Smaller tracks obviously can't spend that kind of money. Down side is that you won't have a "team" finals to attend if that's your bag....unless you feel like towing east of the Mississippi.