That honestly sounds like taxation with extra steps.
Why are you exporting food to some place while the local restaurant is importing it?
The obvious answer is that they both do what is most reasonable for them. If it’s cheaper to source locally the restaurant can (and if they care will) source locally. But why limit yourself to local only?
In practice the “let’s do all local” is very naive. My friend is a farmer. He told me about hay to give you some example. He’s able to sell and deliver truckload of bales for a good price. It’s extra money for him. But the thing is you need to buy truck load. Some local horse owner wanted just one bale. And he explained that if he paid the driver to go over to his farm, load it, unload it, paid the fuel, etc… he’d be actually losing money. So you might be wondering why is that horse owner buying more expensive hay when there’s farm with literal tons of hay not that far away. Well that’s why - it’s actually cheaper for everyone involved.
There’s another company that has cars and equipment to do small deliveries. They buy bulk hay, make smaller packages and sell it, but it’s obviously not local anymore, they need to be able reach across the country as they wouldn’t even cover equipment cost if they only served few local horse owners. It sounds ineffective, but it really isn’t.
I’m not saying that it’s always absolute 100℅ effective system, but everyone involved has motivation to be as effective as possible.
To stretch this into extremes, why aren’t you using locally built computer? It is technically possible to build one in your city. But the investment would be astronomical. And once you produce said computers, producing just enough for local community would never be economical. And if you produced quantities that are economically viable and sold them globally, it would be cheaper to buy them from the local global market than to build logistics for local delivery.