One: the shop often wouldn't let you buy up their whole supply

Two: there are likely other restaurants in the area, so that's 20*N boxes a day

Three: lots of countries have resale laws that prevent this

Four: that's a lot of time to spend every day when you can get a single delivery every week / two weeks instead

Five: the delivery often includes the collection of the used bottles (when using glass) and that otherwise can cost a lot

Any half-sane shop would love the giant piles of money you're spending and negotiate a way to get you a nice big supply with an even easier pickup process than filling a cart.

> Two: there are likely other restaurants in the area, so that's 20N boxes a day

Even better. Imagine a shop saying they don't* want to ramp up to selling ten times as much product out of aisle seven with no extra work beyond staying in stock.

> Three: lots of countries have resale laws that prevent this

If you buy a shelf-stable food, you can't resell it? Why would a law like this ever exist?

> Four: that's a lot of time to spend every day when you can get a single delivery every week / two weeks instead

This is a better reason, but you'd think the huge volume of the sale would get you at least a mild price improvement.

> Five: the delivery often includes the collection of the used bottles (when using glass) and that otherwise can cost a lot

If it costs money to set things out for recycling, the local government is doing a bad job.