Comment Re:Colors (Score 1) 127
For exactly the same reason that you can't fit an infinite number of AM radio stations into a finite width of radio spectrum.
The act of AM-ing a single frequency carrier f_c at data rate / frequency f generates sidebands each side of the carrier, so that the signal now spreads over (f_c - f) to (f_c + f), i.e. the bandwidth becomes (IIRC) 2f.
Fleetie