Why people still refer to Slipknot as a "nu-metal" band?

I know Slipknot included some sort of rap verses in their selftitle album but one would think that after something as heavy as the "Iowa" record or Vol. 3 people would consider them a normal metal band. In "nu-metal" musical talent is not common and an example is the fact that that jewish kid from linkin park or wes borland are probably the most mediocre guitar players the metal world has ever since but in Slipknot and although people don't like to admit it you got to very good guitar players (try to play "The Nameless" or "Vermillion" and see if they are just a couple of power chords) and an insane drummer. Besides while all those bands (Korn, limb bizkit, linkin park, papa roach) are going down as fast as they came up (at least within the metal community because a lot of rappers and wiggers seem to love linkin park) Slipknot keeps rising and putting themselves in the map as one of the most important bands of the new millenium. (BTW, Kerry King said he liked Slipknot)