[FartyMcFarter]

There's a limit to this though. If the food gets cold or otherwise bad due to waiting too long, people will ask for money back or orders will go down.

[munk-a]

Compare this to a restaurant running their own service that can chose not to prepare meals while waiting for more orders to roll in - so the delivery might not be as quick as it potentially could be, but the food is fresher.

[rightbyte]

The main edge the restaurants with their own delivery has. UberEats just black boxes the restaurant excepting it to treat the delivery guy as a ordinary customer. That process has to be so wasteful compares to bulk preparation and delivery.