Because, you know, it is.
For the purposes of being slightly more informative, let's assume that Brütal Legend's imaginative concoction of overwrought metal fantasy and unhinged humor isn't your thing. In fact, let's go ahead and pretend that you've been catapulted right out of the zeitgeist and now find yourself bereft of any cultural joys that could possibly fall under your purview of ownership. In other words, let's say that none of this stuff is your thing.
What you're left with, then, is a third-person action game in the vein of Deity of Disagreement or Demon Might Sob or whatever. The controls are spot-on and the combat is vicious and satisfying, even when your foes have you beaten in numbers or sheer size. Oh, and protagonist slash ultimate roadie Eddie Riggs wields both an axe and an axe in a manner most ... axe-ellent. There, I wrote that and now you can't unread it.
There's a car, too. A radical vehicle which helped me defeat a humongous, slithering worm, took me across a collapsing bridge and then tossed me over the hills of a world that's equal parts Tolkien and Testament. The landscape is home not only to metal album vistas, but soon-to-be-splattered enemies and enormous speakers that double as ramps. If you're the kind to mess around in a sandbox, you'll probably manage to have a few laughs.
And that's really all I wanted to convey to the "not my thing" types. There's a really fun action game here. For the rest of you (congratulations on having a pulse), there's a really fun action game embellished with cheeky metal lore, eye-popping presentation and dialogue that's right at the intersection of silliness and cutting wit. It's like stabbing a clown, I guess.
If you think I'm just gushing and dancing around the game's occasional Pikmin-esque strategy elements (which I didn't play and which I'm honestly uncertain about), then you're probably right. But that's the benefit of the doubt you get when you're a genuinely funny game. My minor concern just doesn't stand up to the firm belief that when Brütal Legend rocks up this October, you're going to love it and make it your thing. If I'm wrong, I'll smash the one instrument I play -- this keyboard.