Steak 'n Shake

I placed my order through the app at 12:01pm with a "promised" pick up time of 12:15. I arrived at the store at 12:14 and showed the cashier my order confirmation. She said she would check on it. She proceeded to serve 2 more customers before going to the grill and asking for my order. The order wasn't even ready! She proceeded to assemble my burgers, chili, fries etc then handed me my order at 12:23pm, 8 minutes after the promised ready time.
What's the sense of providing an online ordering system that promises a specific pick-up time if the promise cannot or will not be honored?