I wish cities should design a delivery railroad. I don't want to let food delivery robots take over pedestrian spaces and having standardised package sizes and weight limits would help make things efficient.
Large cities are designed to get people outside, not keep them inside. A delivery raiload would take up space that could otherwise be used to transport people.
A lot of transportation is required into cities to deliver food and supplies into supermarkets and then homes. If you improved that you'd have more space and time for fun
Objection: most large cities haven't been designed. They grew, usually starting because they had a significant transportation advantage (seaport, seaport + river, river junction, river + pass).