@cicerone imposter,
My point is that you know places and in those places they know you as a tourist.
When I travel to foreign lands, I do not go to hotels, I contact people online and rent a room in the middle of a neighborhood. I learn how they live, what they do. While you visit what the tourist guide wants you to see, I visit the family of the owner who rented me the room.
I will tell you more.
Next time you travel around the world, visit a place where everybody looks like you, if you are white, then a place with white people, if you are black, a place with black people. Try to match the best you can with them.
After that, dressing the same than the people around, walk about 3 blocks from the rental place, so nobody will know that you are the tourist visiting the area.
Learn how to say, "Hey! hello there, what is going on?" in their language. Do it without any accent that identifies you as "different".
Here are some possibilities of what will happen next after you say "hello..." and approach the person with friendly intentions:
1)- the other person will evade you and will cross to the other side of the street.
2)- the other person will think that you are nuts and will evade you as well
3)- the other person will protect himself/herself because will think that you might be a burglar
4)- the other person might smile you back but will hurry going away from you
Now well, this won't happen when you come out of the airplane or ship and say the same words and friendly approach to people and employees in the airport, the hotel, or similar.
This is why, I agree with you that in your travels you have found that you are always welcomed, and no doubt that you have come back with the impression that is a worldwide culture, and yes, it is a worldwide culture to be nice at airports and tourist places, but it is limited. It is not the general culture if you want to apply it in other places where people don't know you are a tourist.
And a warning, you do what I suggest you to do, and by some reason, the guys in that neighborhood know that you are a tourist, beware, because they indeed will smile at you and give you a welcomed hug, and you will return back without your wallet... but happy because you have proved your point.