The EU theoretically defines the goal itself in its statutes about subsidiarity.

Your argument doesn't make sense, you cannot just use abstraction to justify building new layers of governance.

I could give you an arbitrary line and say a common language would be the point. It is sensible as well because nobody in the Netherlands knows any politician from Spain and vice versa. On a national level this is not as pronounced.

I don't need coordination efforts about scanning encrypted messages if that is your question.