I'm guessing the complexity of configurable menu items (pick any 2 of X, add Y for $Z), promotions like discounts or BOGO, scheduling those promos and making all of that easy for the restaurant manager to tweak (from my outside perspective, most restaurants are terrible at it, but maybe that's by design on their part)

on the flip side, there's no intrinsic reason for apps to repeatedly tweak this part of the design. in an ideal world, designers, engineers and product managers sit down, figure it out, and ship. it's not like restaurants are continuously evolving in a meaningful way... but organizations tend to breed this sort of self-fulfilling prophecy where we need more resources to support the increasing need for resources, to paraphrase that quote