Nothing to do with keeping supporters dry . Successive Welsh players have made such a big thing about wanting it shut because it increases the noise and atmosphere in their favour to intimidate opposition , then why do they expect the visiting teams to agree to have it closed ?
If on the other hand they said they loved it open and played better when it was , it would be closed in a heartbeat .
Point is , nobody really cares if the roof is open or closed , but they do care about giving the home side extra advantage