Thinking back on historic nobles - In a lot of ways we think of them as soldiers and tax collectors. But if you read some of the histories closely, you find out about the kings granting this deed of land and that deed of land to the nobles. Sure, sometimes these were just tracts of land filled with sharecropping peasants, but sometimes it was more. Sometimes it was towns or villages. Sometimes it was mills.
I’ve made no secret that the nobles in my world are also merchants. I think this makes really good sense. I think the lesser nobles would have controlled the mills, so that not only did they collect the tax on the crops, but then they also get a share of the profits from milling the grain. This works even better when the noble lord is the soldier and his younger brother is the miller. But extend it - The nobles control all the land so they make perfect ranchers. Think back to the Old West where the ranchers controlled the law in the towns and no one could stop their cattle herds from wandering into corn fields.
In Fletnern, the major noble activity is the crafting of wines. They own the vineyards, they control the serfs, and they are the ones making the wine. Of course, if they produce enough wine to export, they are going to be the ones transporting it, and likely taking others along with them for the ride. After all, they have private armies, why not split the army during times of peace and send half to protect the caravan from bandits?
Don’t stop here. Think of all the commerce driven mainly by land ownership. Quarries, mines, any water powered mill, lumber camps, shipyards. The logic is this: If nobles control most of the land and some guy discovers a diamond mine, wouldn’t the noble who controls that land simply take over, no matter what agreement he originally had with the prospector? And if he didn’t control the land, he’d contact his buddy the king and have the land granted to him and then kick the prospector out. If it’s a valuable enough diamond mine, the king might even send an army to help the noble take that piece of land away from the neighboring king.
I’m not saying that only nobles can be merchants, but when you’re the one who gets to make the laws, why would you be content to simply collect taxes, while others got rich, especially if they might be getting richer than you?