Why are white, caucasion actors the only ones mentioned for major roles in the comic and graphic novel genre??

It seems like with Chris Nolans representation of Batman, and the rise of dark movies like Pan Labyrinths...just the whole fantasy genre in any form is devoid of anyone but white actors. Whenever there are discussions of who should be the villains or the heroes its the same 10 or so white actors...Anjelina Jolie should play every y woman role. Or some anorexic white girl gets to play the mean tough girl, The all american " white knight" is of course white...I LOVED these comics and graphic novels because they represented us all. Now its just about marketing and money...The US has more white people than anything so have it lopsided for white audiences...MONEY MONEY MONEY...Now I am married to a white guy and my daughter is "bi racial" so I could care less about color...But when my daughter asks me mommy why are there no black women in Gotham...I got to tell her about how hollywood wants to make money and white faces sell to a majority white audience...soo that is why...its the truth!