Designers must have rationale. Designers must do things for a reason. Designers must know why. But is this always a good thing? What happens when something just is? I would say, the majority of the time, maybe even 90% of the time, a designer must know why. But there are times when having to know the why ruins the purity. It shackles an idea. Walls off an interpretation. Silos the execution. If it feels like your rationale is doing any of these, best to just let it go. Best to just let it be what it is. That should be enough.