If Kyurem is Legendary,then why doesn`t it learn an awesome signature move?

Question

Glaciate deals damage and lowers the target's Speed by one stage.

Stats can be lowered to a minimum of -6 stages each.

TYPE	 ICE

CATEGORY Special
POWER 65
ACCURACY 95
PP 10 (max. 16)
INTRODUCED Generation V

I asked this because Glaciate is just a bit more powerful than icy wind,which nearly every ice type can learn.

Comments

Neither do Articuno, Zapdos, Moltres, Mew, Celebi, Raikou, Entei, Suicine, Groudon, Kyogre, Rayquaza, Regirock, Regice, Registeel, Deoxys, Phione, Mesprit, Uxie, Thudurus, Tornadus, or Landorus.

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Glaciate is an awesome signature move for regular Kyurem. It both lowers the speed of the opponent, and gets STAB!

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Kind of a bad question :P

Answer 1

Black Kyurem gets Freeze Shock and White Kyurem gets Ice Burn.

Answer 2

Because black and white kyrumen get it. Also these kinds of questions always have the same answer, BECAUSE GAME FREAK MADE IT THAT WAY