Similarly one may ask, what is the point of victory dragon?
If you win a Duel by attacking directly with "Victory Dragon", then you win the whole Match - you don't have to win a second Duel.
Beside above, why are Yugioh cards banned? Mainly banned for it allowing to recycle and reuse your Spell/Trap Cards with effects that can only be used a limited number of times while they are on the field. This is notably the reason that effects that consistently bounce your own Spells/Traps are very rare.
Additionally, is legendary dragon of white banned?
This card is like Victory Dragon, though its banned and the Legendary Dragon of White is not to be used in official matches. Pretty much means this card can only be used playing with your friends.
Is Gandora the dragon of destruction banned?
Instead of "Red-Eyes Darkness Metal Dragon", "Saryuja Skull Dread" would Summon "Gandora-X" from the hand, and to give enough ATK to "Crusadia Equimax", "Guardragon Agarpain" would Summon "Hot Red Dragon Archfiend Abyss" from the Extra Deck. Gandora-X got banned in the OCG in July 2019.