probably because white writers have had no idea how to write a bad-ass, intellectually and technologically superior black super hero. historically, he was introduced in the Fantastic Four, so working them into the next movie would be some nice symatry.

but the best character development has all happened in the last ten years. as someone alluded to above, the US invaded wakanda for vibranium. t'challa and storm married and divorced (and wouldn't BP2 a great vehicle to launch a movie version of storm that finally gets it right). but the best stuff comes out of what jonathan hickman did in his secret avengers/secret war run and, to a lesser extent, what tnc is doing now. in fact, i wouldn't be surprised if disney justified tnc's price tag as idea development for eventual movies.