The K in CMYK is grey, not black. The other ink tones are added to make it appear black.
Edit: It seems people don't want to hear that. But sorry, that's how CMYK works. Black is roughly C=75 M=68 Y=67 K=89 in most major colour profiles used for printing. When you tell your printer to print something black, it won't use just Key (around 85-90% grey), and will apply normal CMYK blacks which use value from all 4 inks.
It's been like this for 120 years and is not a "big printer" conspiracy. If you don't like this, don't use a CMYK printer. It's just going to print CMYK values with CMYK inks like you told it to and none of those inks is black.