Do they? Money is simply the accounting of debt. You do something for me, and when I can't immediately do something in return for you, you extend a loan to me so that I can make good on my side of the bargain later. If we record that I owe you something at some point in the future, we just created money!
But if I don't need anything from you — because, say, magical AIs are already giving me everything I could ever hope and dream of — I have no reason to become indebted to you. Money only matters in a world where: You want/need people to do things for you, they won't do something for you without a favour returned in kind, and you cannot immediately return the favour.