Probably due the fact we rarely mention our race and when we do it is in writing it in or checking it the box we are being instructed to fill out.
Even then there is no White box to check only Caucasian.
White is weird since we really are not white, we are pink, different levels of tan somethings, fair but not white, greenish gray when it is the liver and gallbladder gone bad, orange brown when it is cirrhosis of the liver.

Either way you look at it we are not White we are like chameleons our skin color changes according to our health and activities.