The more Daggerheart games I'm running, the more I'm coming to realize that Fear is a psychological currency to facilitate making crap up. I say this with kindness and humor. As a GM, I always have the power to make crap up in whatever form I think is both fair and fits the narrative, but the currency of Fear does a few things:
The players can see how much Fear you have and watch you spend it. This makes the nonsense you do feel both justified (because you paid for it) and limited (because you only have so much Fear). People are often more tolerant of the GM making crap up when they think there is a bounded amount or trade-off happening.
It helps absolve you of any potential guilt you might have for making crap up. If you had any lingering doubts about adding an adversary to combat just because you didn't telegraph it? You think the hallway could use a good gas trap right now even though you didn't put it in your notes ahead of time? Begone guilt, the rules of Fear say you absolutely can, AND you're spending currency to make it happen!
So Fear isn't giving you anything you didn't already have as a GM. It just pats you on the back and says "Go ahead. Spend a few of me and do that cool thing you want to do." Then it whispers in the player's ears "That thing he just did? It's cool. He paid for it."