Exactly. The Centurion is basically a card for those people who see money like something like water, that they have in such abundance that it loses all meaning to them in the way we see it. They rather see it as a medium that they can use to refresh themselves, especially since they have it in unlimited supply. It is for those multi-gazillionaires like ruthless tycoons, oligarchs, sports or entertainment megastars, tech and Fortune CEOs and board members, oil-sheikhs, old European money, and so on. The elite of the elite whose net worth must start at at least a billion, USD.
The Centurion card is not for those who want to collect MR points and redeem them for air tickets, even First Class. It is for those who would feel like buying the entire plane using it. It is for those who happen to spot an art piece costing $10 million up for sale at a gallery and order their concierge to "put it on the card". It is for those who would want freshly squeezed orange juice from Marrakech delivered to wherever they happen to be every morning. It is for those who would want to place a recurring charge to maintain their fleet of supercars at Maranello or their teams of race horses in Kentucky, or to pay docking fees for their yachts in Monaco. It is for those who are so rich that it is ridiculous and a crime.
The Centurion is not designed for even your regular $ multi-millionaire and certainly not for those who are hands on running businesses or worrying about their paychecks, just like an Infinia is not designed for a call center fresher, and just like how the Platinum card is not designed for me, I am very well contented with the Gold. It is designed for those who simply wouldn't even want to waste their precious brain time bothering about the 3.5%, they probably earn that amount back ten times in the few seconds they spend to think about it. And as for lounge access, the typical Centurion probably flies private.
And well, Amex realises how well (or not) they can earn from each customer and probably serves them accordingly. They shouldn't, but as they say, that's just business.