In my opinion, this is just a pretext to extract more spending. This is part of the way that American Express generates profit from Centurion. They use it as a carrot which motivates people to spend more on other American Express products. American Express also knows that people place a higher value on things they have earned compared to things they were given. Making someone earn a Centurion card increases loyalty, and perhaps lowers resistance to fee increases or benefit reductions.