At the time they wanted to try doing something for the new players who might feel that there is no way to compete against old established players. (it seemed like an ok idea... they haven't really continued with it though, other than having the 2 "rooks" in guild events)
It was meant as a rank reward to rookies... like actual -new- players.
In order to prevent old players from just making an extra account, going into the rookie competition, destroying everyone, and taking the rewards... they made it so that the rookie rewards cannot be traded... so even if you win them with a new account... you can't actually transfer them to yourself.