Some say they dampen the performance, and prefer the 'feel' of an uncovered bat. I have no idea which one is right, but I do believe that scuff sheets help to keep performance for a bit longer, (As the impacts are dampened slightly, therefore damage to wood less) and definitely help preserve the bat itself. Entirely up to preference, I think some people just enjoy looking after their bats without scuff sheets, as it doesn't hide any cracks, and you can clean the bat regularly with an oil rag. (Loved doing this with my old Adidas Incurza)