Most fast food is largely cooked to order and pretty rapidly degrades once you try to hold it for more any real amount of time before consumption. /Maybe/ partially assembled burgers could have patties cooked right before serving or for pizza do a model like the pizza vending machines where it's baked right before it's dispensed but I don't see the version becoming popular where it's a lot of food fully precooked and assembled being predictively shuttled around town.

Beyond quality issues it'd just lead to a massive amount of food waste too. In order to always have the order available you'd have to stock everything in excess of demand and food only holds for so long before it has to be disposed of for safety reasons.