Dirty dishes issue, is it some bug or just game mechanics

I haven’t experienced this as of late, tho it has happened in the past. What I do see all the time is that despite having an expensive, amazing and handy sink in the kitchen my sims choose to go out of their way to wash them in the bathroom sink. There’s nothing obstructing their use it of it either because they will use it from time to time. ??‍♀️