Howling Abyss Snowball Throwing

Quick question, why are we not allowed to THROW the snowball during movement restricting CC? (snares, roots, and POSSIBLY Cassiopia's new Grounded mechanic, I added that one because it makes sense to count it) I mean I understand not being able to use the dash function of it, but why are we not allowed to throw it at all? Honestly that doesn't make sense.