It's not profitable because every single restaurant does it for itself only.A post office service would never make a dime if it was only covering a small town.Scale it up to the entire city and it becomes very interesting
Back in frontier west, outside US territory (and therefore not served by the Post Office Department or the Pony Express), people would set up highly profitable transportation companies. These companies would make deliveries for local shops but also carry mail, bringing stuff to somewhere served by the Post Office Department or the Pony Express or the Wells Fargo freight routes.
I read all this in a book ages ago but I was skimming through some wikipedia articles that mention some of what I'm talking about if you're interested:
Yes, I understand economies of scale, but there is a point where the time and resources spent driving take-out around is not profitable. That's what I mean about certain restaurants and cafes not offering delivery, because even with a third party full time delivery service it's not profitable to deliver certain goods.
