I don't see insight as a social or charisma based thing. Can you watch a movie and get a feel for whether the actors are depicting the emotions and thoughts they are experiencing? Anything you could measure without talking to or being seen by your target (subject) isn't a charisma based...
Sorcerers useCharisma as their primary Ability Score for spell-casting in Dungeons and Dragons. Wizards use Intelligence to cast, and Clerics use Wisdom. Intelligence and Wisdom make sense for the respective character classes, both mechanically and flavor-wise. Why is Warlock Charisma based? Charisma...