Yanno.................I've been on both sides of the fence, and not only here in the U.S.A., but overseas as well.
If a person was nice to me and told me about the specials, as well as recommended what was good (as well as told me what wasn't so good), I'd tip them around 15 percent. Why? They talked to me and made me feel welcome in their establishment. Incidentally, the people who made me feel welcome were pretty much outside of the US, because most of them were in the countries I'd visited as a U.S. Navy Sailor.
Yeah.......................you're right..................most people who serve you are inclined to take special interest in those who aren't from the same place. When I was a bartender and a cook in various places in Amarillo, I took a special interest in those who weren't from here (and got news for you, there are a LOT of foreign visitors who come through here), because I was interested in where they came from, and how their culture was similar to mine. Tips didn't matter, shit...............sometimes the beers I bought for them cost me more than what they tipped, but the stories were golden.
I say that tip the people who make you feel welcome the same amount as what you feel they made you feel welcome. Sometimes, my room mate and I will tip the people on the drive through, just because they were nice and made us feel welcome.
Sometimes, the people who serve us at a dine in place are snarky and sarcastic. Those people don't get much of a tip.
BTW....................do any of the people posting on this thread about lobster realize that originally it was considered "poor food" much like beans and rice of today?
Lobster was originally fed to the slaves and the poor. Ironic that now it's become a delicacy, but, if you live where it's abundant (like up around Newport RI or the Maine coast) it's pretty cheap.
I know, because back in the late 90's, when I was stationed at Newport RI, you could get a 1/2 pound lobster for around 5 bucks on Lobster Friday at the Petty Officer Club.