Saving Throws

[Roman]

Just wondering--not challenging, but genuinely curious--why were the following saving throws placed under the umbrella of their given attributes:

Wisdom: Polymorph, Petrification

Charisma: Death Attack

Just wondering what the thought and rationale behind these choices may have been--I can see why most of the others work, but I'm still puzzling these through. Not so much because I want to change them; I'd just like to know the design decisions.

Thanks!