Yes it is unfair to get the shine, it should be natural, same way spinners too should not use soft mud or the soil from the pitch to get extra grip over the ball, many spinners and fast bowers uses both which is incorrect and un-natural it is totally unfair on the part of the bowlers to use saliva. soft mud from the ground, the " ball tampering" code should be used here, even the rubbing the ball on the cricketers clothes to be disallowed.
