Let's consider a US buyer of Parmesan: I have a choice between regular "Parmesan cheese", which is held to no particular standards in the US, and "Parmigiano-Re

Let's consider a US buyer of Parmesan: I have a choice between regular "Parmesan cheese", which is held to no particular standards in the US, and "Parmigiano-Reggiano", which is both expensive and (IMO) predictably delicious. Parmigiano-Reggiano is good because there are regional standards. As a customer, I know what I'm buying. This is the whole idea of a brand: It provides useful information to customers. In the case of champagne, I'm usually unwilling to pay for the regional "brand." Instead, I often buy "cava," which is another regional AOC for sparkling wine, this one run by producers in Catalonia (and elsewhere in Spain). It's a bit cheaper, which is probably less than ideal for the producers, but I still know more or less what I'm getting. You could argue that one or the other of these two situations is less than optimal. But as a customer, I find that AOCs and DOCs generally help me buy products I'll like. And since it would be hard for the producers of "Tennessee Whiskey" to enforce their agreed-upon quality standards on a company in New Zealand, it does make a certain amount of sense to limit participation geographically.