You don't have to give a crap about dancing ... to give a crap about Rumer Willis emerging as a major piece on "Dancing with the Stars" -- although you'd have to watch the damn show to know that.

As we've said ... she doesn't need the Mirrorball Trophy (but she'll probably get it) -- Rumer's already won the Now Everyone Knows I Have a Bangin' Body award.

Exhibit A: this outfit with the neckline down to her belly button, and the leg slit up to her ... ya know.