How childish. It's not my fault you fail to see the equivalency of trade missions and privateer missions in this game.
Trade is an exchange of goods and/or services. When you increase your trade power in this game, you're not exchanging goods, you're making yourself richer and if anyone else is affected, it's to be made poorer.
Exactly as the person above me said, you should see trading in this game as something that happens behind the scenes. You are not actually in control of the merchants, they do their things regardless outside of state supervision. What you are in control of, is making it a lot harder for enemy (other nations) merchants and a lot easier for your own until you are able to tax all the trade going through a region and the other nations cannot. That is what 'trading' represents.
It is a pure pvp system about, indeed, stealing all the taxes generated from trade from your rivals.