Here's a few of my reasons for washing Microfiber-towels (MF-towels) before they are initially used on my vehicles:
•I think about from where almost all Microfiber towels originate: Korea; China.
-They must be transported for long distances in a ship's hold; or in some airplane's belly; in the back of some delivery truck...before they reach my vendors/resellers
-They are transported alongside/on top of/under/with "who knows what else items"
•To remove:
-excess chemicals from the MF manufacturing processes
-loose threads (from cutting the MF)
-sewing machines' oils
-oils and dirt from the hands of the factory workers
-contaminates from MF being dropped on floors, etc., during manufacturing/packing/shipping
-outgassing from plastic packaging material
-etc.
I say: Wash 'em first...Why take the risk?
Bob