From what I briefly read, a large chunk of Pantone doesn't even fit in CMYK:
> About 30% of the Pantone system's 1114 spot colors (as of year 2000) cannot be simulated with CMYK but with 13 base pigments (14 including black) mixed in specified amounts.
These 1114 spot colors are apparently themselves only a part of the total 2161, but still it's 400 colors missing, seemingly without even accounting for texture effects and whatnot.