That's a pretty grandiose title for a pretty simple thought I had.
I think that in a game where you can buy significant adventuring power, you end with a choice between:
- upgrade my PC with magical power
- upgrade my PC with mundane power
Buy some magical power at the magic shop, and you are better at adventuring. Especially in those areas where merely adding more manpower (hirelings, henchmen, etc.) just won't matter. All the crossbowmen in the world won't help much vs. weapon-immune demons or when you have to crawl down a tight corridor to face a lich in his lair.
Spend those resources on establishing a fortress, hiring guards, etc. and you expand out in the political world.
In a game without the ability to spend loot on dramatic personal power upgrades, you start to automatically get drawn into the "domain game."
But in a game with only one, you've essentially made the choice. No magic shoppes or NPC enchanters? Loot is useful mainly for expanding your non-dungeon power and your control over the larger campaign map. Have them? You can get personal power.
In fact, having them is a strong signal that the intent of loot is that you upgrade. If building a fortress or hiring some guards and henchmen doesn't help you adventure better, but magic swords are for sale, you're saying that you're handing out loot so people can buy magic swords.
In my current game, buying additional adventuring power is the name of the game. Wealth is a tool for the players to expand the power and resources of their adventurer's personal abilities. While we could expand the game out to be "establish a domain" I'm not sure we ever will. It's a feature, not a bug, and I have to remind myself of that when people think of the best cash-based upgrades they can get when they hit a large pile of loot. $200K worth of gold and silver isn't a downpayment on the walls of Mi'Pee'Cees Castle; $200K is a signal that you darn well need $200K worth of magic upgrades for the upcoming adventures.
In my past games where magic was only found - not made or sold - mundane power was where the money went. PCs own inns and taverns, cleared mini-dungeons and lived in them, cleared haunted mansions and lived in them, worried about getting to name level (in D&D-based) or enough cash flow because they wanted followers, and so on. That's pretty much what money was good for.
I don't think this is a good vs. bad issue. It's just that I feel like allowing magic item purchases might be a signal that loot is provided so you can upgrade your personal power. Also, people tend to worry about winning the last war. So even if upgrading personal power isn't the endgame, if lack of it made the previous adventure hard, then it's reasonable to expect they'll spend on personal power.
It's possible circular as well - play games where you don't really have a "domain game" as a goal, and people start to wonder what all the loot is for. Let them buy some personal power, and then loot becomes all about it. And vice-versa - play games where "domain game" is the up-front goal, and personal power isn't easily for sale, and people will gravitate the other way.
Just something I was mulling over while thinking of spending habits of PCs in my own past games.