I can see why; doing something useless requires conscious thought / effort. Doing something you want to do / achieve / change is, controversially, difficult because you think you can rely on just you "wanting it", that is, innate motivation. But that's usually not the case, especially not if it's something that causes discomfort at first (like going to the gym) or if it means giving up or cutting back on something pleasurable (mmm, donuts).

But intentionally doing something that you don't do normally, something you don't want to do, something that doesn't give you any kind of dopamine feedback can help you practice forming habits, practice self-discipline, etc. It's an interesting experiment.