In that case, why not use Surf over Scald's unreliable 30% chance to burn?Cute Charm Moonblast vs. Pixilate Hyper voice on Sylveon?
Technically, Cute Charm can be used to your advantage along with Moonblast's unreliable 30% chance to lower the opponent's SpAtk. However, it seems completely inferior to Hyper Voice which is significantly stronger and hits through subs.
That plus Soundproof utterly walling certain Sylveons if they use PixieVoice gives it a niche, and even a little niche is all it takes.