It’s not so much that dust bothers me but I have read that dust can effect the actual speakers themselves thus effecting the sound quality. Otherwise I never put things in there cases. All my high end guitars hang on the wall for me to enjoy where many guitarists shudder at the idea.
I like the look of the Focals hanging on the rack. A good percentage of my purchase decisions are often based on aesthetics. So I tend to lean towards the leave them out camp but I still wonder about it.
I have an older pair of inexpensive HIFIMan HE 400i's which I never put away. They do still seem fine.

