First, here is the bass by itself. Sounds pretty nasty and grungy, right?
Next, throw in the (fake) drums with it, it starts to lose some of the edge.
Up next we get the doubled rhythm guitars; the bass sounds less and less distorted, but you can still hear it, and it fits in pretty well despite the initial sound:
Finally, all the parts together.... Warning! Layers of fuzzy guitar solos and harmonies ahead!

By this time the bass sounds almost clean. Go back and listen to the first snippet, just the bass. Sounds nothing like it does in the full mix. How 'bout that?