He is. If you really start to listen to the blues (especially Delta) then you know that he's one of the kings... the pillars. Before anyone heard of Robert Johnson, Skip James, Charrlie Patton & Son house were recording what we still consider legitimate blues classics. He was one of the few to get to that wider audience at the end of his life. A great many didn't.
Skip James was an incredibly talented guitarist and his singing is clearly in a much closer vein to the folk and blues singers to come than many of the better-known vocalists of his generation. Why isn't he revered?