I think people are placing too much on this. Being registered is just sending a piece of mail with a checkbox checked, I think. You don’t even have to donate or anything. I registered as a Republican to vote in their primaries a long time ago, and I have literally never voted for a Republican candidate for any office.
My city has both, and they’re decorated the same. I just wonder whether a really good burger place did this first and then crappy ones showed up to copy the decor and forgot to make the food good.