I wonder how quickly airlines will adopt sanded/rough wings. It's also interesting that the efficiency of winglets were known for quite awhile but only somewhat recently have nearly all airliners adopted them.

It’s probably operationally easier to keep surfaces smooth than to keep them a specific amount of roughness.

Modifications to an approved type design, especially for commercial passenger aircraft, are an intensely bureaucratic and thus very expensive process. This is part of the reason why product cycles are long.