Pathfinders need Cha-based skills, particularly diplomacy, in *every* scenario, whether it's to get info at the beginning using gather information, or by talking to NPCs later, or to achieve the whole mission. There is no other ability score that you are guaranteed to use every game, since there are now (a few) scenarios that don't require combat at all, but there are none that don't require talking to NPCs and gathering information.
That is a significant overstatement. There are lots of scenarios where diplomacy has no significant effect and I've never played one where nobody took any damage (is, con is always useful).
Also, you pretty much only need 1 character in the group with good diplomacy.
That said, LOTS of my characters have good charisma and social skills. But that is because I LIKE interaction, not because I NEED to