The Deacon is of course correct, as usual. I'll expand on his answer a bit.
Think of dust, as tiny little sponge particles. Dry, becasue they floated/made their way there into/onto your knife liners (Dry cotton bluejeans lint).
They then easily soak-up moisture from the surrounding air (think steamy Summertime pockets, or a humid day), and then they hold that moisture tight up against your liners for hours. Possibly thousands of hours? At some point, even some of the best of stainless
steels start to show signs of corrosion.
I am lucky enough to be walking by an air compressor hose, nearly every hour of the day. I blow my liners out, and the end of most days. If you are not as lucky? Buy a can of compressed air, and give them blast. At least once a week.