I understand why women typically can't compete with men in most sports. There is a strength/size factor that just really makes it impossible for women to compete at the highest level with men.
However, I have never understood why women typically don't compete with men at the highest level of auto racing. I know there is a grueling mental aspect to a race, but there is no difference (that I know of) in powers of concentration. It is also physically grueling to race, but it is more of a drain on the body than a requirement for brute strength or speed.
I think Danica would rather people not say "this is momentous, a woman has won an Indy race." Instead, I would bet that she wants to hear "this is momentous, a race car driver who has been close before finally broke through, and will certainly win again."