Sampras didn't not get love because he's white. He didn't because he was boring. Agassi always got recognition and had the fame because he was stylish, he had style, flavor, whatever you want to call it. Dirk doesn't get the national recognition because he hasn't quite earned it yet. He's gotten no rings, he plays in Dallas (not NYC, Chicago or LA) and isn't flashy either.
But your premise isn't completely unfounded.