Don’t be a dick and be nice are more about being respectful and understanding than following etiquette.

I personally know people that would argue etiquette is a form of kindness. They unironically think there’s a connection between where the spoon goes and murder. This is of course not true, but the ability to transcend your own cultural context and look at humanity as a whole is surprisingly rare.

If we could all do that, then maybe specific rules would always be unnecessary. But again, that’s not my lived experience.