Friction
The reason that perpetual motion machines don’t work is friction. No matter how little energy you think is being expended in the process, there’s always a part of it that’s losing a little bit of that energy, a little bit of that effort, in the process of just working. If a wheel turns, some of the energy it’s using turning is gone thanks to being spent on the process of turning. No matter how clever or cute your system may look, if it’s not getting energy from somewhere to overcome that energy that’s going somewhere, you are running down.
This happens in games, too. I’ve been playing some old dos games, and the interfaces are often the things that I really struggle with, because just the mental effort of getting used to using those buttons to do those things and get used to how it wants to work is a flipping chore. War Wind is a real prize of an old RTS – heck, almost all RTSes are like this – where the lack of things like shortcut keys or even a map that responds cleanly to ideas like dragging and dropping is a huge pain in the ass. Memorising all the shortcuts is the best option but then that’s the same kind of labour. It’s friction.
In tabletop games this exists too. The math you have to do to resolve a combat is friction, and I think that 4th Edition D&D does have a bit too much fiddly friction in its feat system. Specific clausal conditions generate that friction, they lose player energy and effort.
Shuffling is friction. I love Sector 86, but no lies, every few minutes every player sits around waiting for the deck to have a good ole shuffle. Fetchlands in Magic: The Gathering are awesome, but they also add seven minutes or so of time to an otherwise unremarkable match of the game.
In games, you are asking your players to put in effort, and some of that effort is spent in places. If I am losing effort on the things that don’t feel rewarding, I am spending energy managing existing.
This is, incidentally, part of why depression is so rough on people’s lives, in case you needed another useful metaphor to help you not treat people with depression badly.