Sheep Skin has a very fine and smooth surface texture!
How should clean your precious watches, by using your cuff, your silk tie? Your handkerchief!? Tissues paper!? Worse is Tissue paper can could scratch your watch! Don't do that!
How about Eye glass cleaning cloth made with polyester!? Or simply a piece of sheep skin!?
Anything would not be soft enough as the sheep skin, and it does not create abrasion that result with scratches on your watch, It cleans and will not leave a trace of oil like film on the crystal!
The Sheep skin is having some super soft tissue and it does not hold tiny metal debris, sand, whatever that would leave the polished surface of your Rolex a permanent mark.