There's an interesting pattern in some cases where the meaning is not made clear to the leaders of the nations. The instances we have recorded are ones where prophets are present to interpret them for them. There may be cases where the meaning is not hidden, if there are no prophets with the gift of translation.
The principle is a good one – events that happen in our lives can be explained with spiritual discernment, which we may need to rely on non-secular sources to understand them.
The Pharoah has his dream of the seven cows and seven stalks, which is the Lord telling him the status of his kingdom in future years, and what to prepare for. He is receiving revelation regarding his stewardship.
Moses and Aaron are set apart to speak unto Pharoah.
The Lord sends a dream to Nebuchadnezzer about the latter-days and kingdoms.