E.g. older houses were hand-built, but nowadays houses are built with straight walls and standardised heights for everything so that mass-produced furniture can fit in them. But if in the future our furniture is made on-demand by AIs, then there's no reason to do it that way; you can have a non-standard height for your kitchen counter (for example) and if/when your dishwasher breaks, the AI system will fabricate you a new non-standard dishwasher to go under it.