LOL.
But many folks use them in certain environments.
If you work in a body shop the body filler dust and primer dust is a light color and really loves to mess with darker colored boxes and covers so many opt for a lighter color.
If you work in a welding shop or metal shop metal grindings and metal dust tends to be dark so it messes with lighter color boxes.
Paint overspray of running a shop with a paint booth or even just open spraying on the floor, produces overspray of all colors.
I see boxes covered if company owned with tools that are not used often all the time.
On our production floor, prototypers, engineers and mgrs. that have boxes on the floor but don't need to access them daily often cover them to keep the welding sparks, grinding dust, paint overspary and the like at bay.
I have a good friend that owns a body shop and since he spends most of his time in the office, covers his box to keep the overspray and bondo dust out. Once that **** gets into the cracks and especially the dwr. slides it's a bear to get out.
If the box just living in a home garage, basement or std. lube shop or auto repair shop, they are usually dust free enouff to not need a cover. Grease, oil and lubes are the enemy there. Move up to industrial environments and mfg. and the need for a cover becomes more obvious.
As for cleaning the cover, windex aka glass cleaner is the easiest to use on our production floor. Cheap and dries easily and gets the dust off. We move up to 3M adhesive remover or Naptha to get solvent based stuff off including paint and glue overspray.
Covers usually become a PITA for daily use, but do have thier purpose.
Good luck.