In my experience they vary considerably across languages and cultures. I suspect they are important language constructs in cultures that aren't inherently blunt

In my experience they vary considerably across languages and cultures. I suspect they are important language constructs in cultures that aren't inherently blunt. For example, as a British English speaker expressions like "I'm sorry to make a fuss, but..." are there not to enable lying but to express humility. Sometimes. There's always exceptions of course.