I have some questions about the hexblade Warlock!

Hello Faerûn,

I am playing a hexblade warlock. I always cast the spell, shadow blade which gives me 7-28 damage at level 6. I am aware I can make this scale with my charisma by casting bind hexed weapon. This is my primary weapon I use with booming blade and all other attacks.

Is there a reason why bind hex weapon just isn't automatically applied? Why wouldn't you ever want this ability active?

Second question, why would I ever use pact of the blade? It seems inferior in every way....?

Thank you for your time and input.