BK is actually one of worst examples for granite.
But if around 20 ls'es from various adventures (RB, VtV, SotV, Outlaws) don't yield granite in even 1 case it's closing to statistical miracle. Those adventures have chances between 25-33% for granite drop so should get about 4 in 20 in average case. Getting 1-2 in 20 would be unlucky. 0 is... very bad luck all around. And I'm not only one getting similar results.