> it's completely rational to want to maximize a resource
Sure, in a video game where you have one attribute and you can minmax a strategy just focusing on that, but that's not how real-life works.
You can't just stack pending work on top of each other, expect yourself to be able to stay equally on top of everything and have the same results as if you didn't. With this comes the consideration about the tradeoffs of "produce mediocre but large body of works" vs "produce high quality but small body of works".
Who's to say what's more "rational" or not, it's not a straight-forward calculation which culminates in "Must consume all available usage to maximize resource usage" like some robot, as we are not.
It's quite literally inventing work out of nowhere as you wouldn't put the agent to do that and forcing yourself to be conscious about that work until it completes, unless you actually had the usage available. Asked another way, wouldn't your workflow clearly change if you had unlimited usage available? You'd probably attack tasks/problems that you didn't consider actually spending time/energy solving.