Seems a bit arbitrary :) Which it is in Europe as well, e g. the essence of Wiener Schnitzel is not that it's from Vienna, but that it's made from veal. Same preparation using pork may only be sold as Vienna-style. Come to think of it, Wiener sausages don't have to come from Vienna either...
I think it's just a question of how the popular parlance evolves. Band-aids aren't just made by the one company anymore, earlier I "googled" something using duck duck go, and when I get sick I usually buy generic kleenex at the store.
I'll buy the store brands of colby cheese and muenster cheese, but "New Jersey Blueberries" are still a niche NJ product.
This certainly plays into it. From my understanding, part of "owning" a brand is actively protecting it from generifying (generification? ... keeping the brand name from turning into a generic designation). If a term becomes synonymous with a class of product, it's no worthy of trademark protection.
That's why companies are fairly protective of their brand names and insist that you use phrasing like "Scotch Brand adhesive tape" and avoid using the verb "to google".
Terms like "Escalator" and "Zipper" fall under that category.
On the other hand, even though you may think "Kleenex" is a generic term, good look trying to sell facial tissues under that moniker.
