[narkotic]

Well it could be.

Take for example, the Kurenai Joukai are to be known as a very polite people who have a deep sense of honor (No need to make comments about the state of things at present, not all kingdoms are at 100% of their desired descriptions). One of the leaders of another kingdom, or members, does something which insults the customs of the Empress of Kurenai Joukai. This leads to demands by the Empress to the leader of that kingdom. The leader doesn't understand the importance, so makes light of the punishment. To the Empress it is a major deal, and should have a severe punishment and is insulted by the lack of care shown by the other kingdom leader.

Silly as it might sound, many wars were held over the same reasons. Alliances could fall also due to that. If your ally should not care to learn the parts of your culture, and show respect by following some of these customs in your homeland, then what reason should you have for allying with those people.

I agree with you though, economics does not currently play a part in this game yet. There are diverse food stuffs available in shops. If somehow this was changed (and the shop didn't have all that food stuff) and it was available only in the separate kingdoms, trade could be established, and control over supplies could be issued. It'd be interesting to see what would be done with that.