I would think this is largely because the resolution of political drama is not easily represented by arithmetic unless you would desire a social combat system in which social interactions are abstracted to a mechanical challenge rather than an intellectual one.
As a salesman by occupation and a fan of political discussion, a lot of social interaction in D&D would be arithmetic fights.
The core issue is that you'll be investing system resources into a system that some playstyles straight up ignore, some playstyles could us but the
players straight up ignore, and some playstyles that have different levels of need.
It's the "Mental Stats" problem.
If you are in a pure combat table, Intelligence and Charisma are useless dump stats for anyone but the classes who use them for magic.
If you are in a combat heavy table, Intelligence and Charisma are still useless dump stats except in a few clutch situations where your DM forces a single check that ends up being a big deal.
If you are in a combat light but freeform table, Intelligence and Charisma are
still useless dump stats except in a few more common clutch situations
If you are in a combat light table where people are sic of the dump stats, Intelligence and Charisma become powerful as the DM has added a few powerful optional rules or force mental skill checks often.
If you are in a combat extra light table, Intelligence and Charisma are
overpowered because of a fat book or pdf file.