That gets to the fundamental nature of the Dungeon Power though, as opposed to the setting more broadly. Like, if it's an alternate reality demiplane with like hologram monsters that drop gold nuggets when you beat them up, then that's only useful for moneymaking, but it's a way to turn violence capacity into money that isn't just like... crime.
So you could do a thing about Dungeon Creating Person recruiting people who have powers that are mostly good for doing violence, and giving them a place to use their powers that isn't just like... knocking over banks. Do a found-family thing where teenagers with evil-coded scary violence powers get to cut loose and have fun with their powers in the dungeon and get gold nuggets out of it, on top of that.
Well conversely if we just view the dungeon as a mysterious door, it's "use" is whatever you can carry back out the door, so it's just up to you to define by fiat how the portals would be useful. The obvious, gamer-like thing would be that it has unique drop items that are unique treasures, like Healing Potions or something, that can be taken out.
Another gamer-like thing might be that successfully completing the dungeon results in "Leveling Up", like... completing the dungeon makes your Special Power more powerful. So as the Dungeon Creator successfully completes dungeons, they can make bigger, harder dungeons. To wit, harder than they can complete alone (thus, they need to recruit party members now). And then it turns out other people who complete dungeons see their powers improve, so the "Usefulness" here is like, a power-improving meta-Power.
