I'd heard that lined styles can draw in dust, dirt, grit etc.
It's actually the exact opposite.
Unlined holsters hold any particulate matter in the "fuzzy nap" of the flesh side of the leather,,,
The dirt particles act as an abrasive to a gun's finish.
Suede lined holsters are probably the worst on a guns finish,,,
It acts like the cleaning rags you buy that are impregnated with a mild abrasive.
Smooth lined holsters are the easiest on a guns finish by far,,,
There is nothing for the particulate matter to imbed into.