Try sliding a finger over a gloss wall tile, then a satin one. The squeek of clean glass is the grip grabbing and slipping.Anyone who has worked in a body shop will tell you a gloss finish has more grip than a satin one. Think of a tyre, the grippy race ones are slick, treaded tyres have less contact area hence less grip unless its wet because the tread removes water leaving less contact than a slick in the dry but much more than a slick with a layer of water between it and the tarmac. Make sense?