Earning regional wealth in Manor Lords is important if you want to purchase livestock, build workshops in burgage plots, or provide fancy treats for your peasant populace so they won't notice you're taxing them into the dirt. While your treasury is filled with tax income which you use to hire mercenaries or build settler camps, trade relies on regional currency instead.
If you want to trade, you'll need something to… well, trade. Success in Manor Lords is about harnessing abundant resources; what do you have and how can you use it?