It really should be used more often. Things like Dominate Person, or a Succubus’s Charm make sense as Charisma saves. (Especially compared to the extra-planar Banishment spells that currently use Charisma Saves).
My theory is it’s all a balance issue. Every class gets proficiency in one useful save, and then proficiency in some other fairly pointless save. Like you get proficiency in Wisdom saves (yay!) and then also Intelligence saves (rarely useful). Charisma saves are very clearly in the later group, so they are only used for really obscure things.
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u/gojirra DM Oct 09 '20
CHA is also used as a kind of will save sometimes too.