Darth Hade said:
To tell the truth, I never liked the look of "the cave" in ESB. I didn't like that it looked like some sort of hidden or long buried structure. It should have just been a cave, nothing more.
While I've never wanted the explanation, I've always liked that there was a structure there. It hinted at something ancient and mysterious. Implied a richer backstory than we'd ever get to know.