D&D is primal fetishism. It makes relics out of old character sheets and totems out of a stack of hardback rulebooks. The dungeon crawl itself is a ritual with no obligation to make sense beyond the circle of participants. In that sense, it's a lot like a cave painting of some ancient hunt. It's a convergence of random events in a controlled setting that forms the basis of a heroic tale in the minds of the participants. Powerful and primitive social magic that can't be reliably explained but only experienced. And IMO, a much more 'real' experience than the forced plot you see in most 'storyteller' games. (see the whole thread here).
I would go on to argue that the dungeoncrawl is D&D in its most pure form. It's not simply a repetitive, childish hack and slash (although it can be). When done right - with both intelligent, experienced DM and players, the dungeoncrawl can be every bit as cryptically meaningful as a Thomas Pynchon novel. Wilderness adventures carry with them a whole set of expectations about reality which a dungeon does not. The dividing line between the adventure site (the dungeon) and the non-adventure sites is clearly drawn - even a child understands that going through that big skull gate into the underworld means serious business.