Its called marketing folks.... These hotels know that if you are a Centurion or Plat member you have enough income to justify their rates. They want you in their hotels and they are willing to pay to see you come in the door. Its better exposure then say RC going out and buying a 2 page spread in Conde Nast.

As for the whole rate thing, a lot of hotels (specially europe) just match the FHR rate with other corporate rates (or rack) and add the breakfast bonus. North American hotels tend to play the rate game a little more. It has nothing to do with commission rates.