[BC] need a NON-technical explanation

[harold stanton]

All et al;
 Not to show my age but...................
 When all this began, please remember that true single frequency control had yet to be developed.
 Operating "close" to your "assigned" or chosen wavelength was done with a free-running oscillator.
 Crystal frequency precision came later on, then the actual frequency could be specified and  be expected
to be tuned properly. The Kc assignments came as the band regulations evolved to reflect this improvement.
   Harold Stanton
American Broadcast Consultants