Why does the MPAA even rate films

Rating: 8/10 (10 October 2003)

Number one, I like this movie very much. After the tired explosions and blah direction of this summer's blockbusters, this is a breath of brisk autumn air. I gave it 8 of 10. Little plot, great action, wonderful looking!
Now, does this mean it should be seen by everybody in the "R" realm? ABSOLUTELY NOT! This is a tough, brutal film to watch. To quote David Strutt in a previous review here, this is "fight porn".
Many others here will tell you how great this movie is viscerally. Blood as paint, perhaps. I just feel the need to add how brutally non-stop the graphic violence is. The body (and limb) count is extraordinary.
So my question is, if this wasn't Quentin Tarentino, would this have been released in its current incarnation with an "R" rating? If so, this is the most violent film I've ever seen with such a rating. I don't see how this is even in the same ballpark (or planet) as Woody Allen's "Anything Else" which was also graced with an "R".
Maybe it's time for an "R-17" rating, since "NC-17" seems to be taboo. If we are going to have ratings at all, use them as they should be used. "Kill Bill" should be "NC-17" Period.