curby is a small sprint track
if someone was to take my car for a run, i wouldnt like it to be at an air field where you could ring it out in all the gears, misjudge the speed (ie hit 150 when youd normally only see 100) and then totally mess up the braking and crash it
an air field is a dangerous place even in your own car as the wide open space skews your perception on the speed... put someone in a much faster car and youre waiting for trouble
curby is small, much smaller speed, much reduced thrashing, its ideal