First off I don't like the way you've associated communism with socialism, the way it was phrased makes one think the terms are interchangable, which they aren't. Socialism is distinctly different from communism, though sharing qualities.
Kusari is more akin to a feudal shoganate, which is the direct model used by the developers to create the governmental system. And it already its oppositional slots filled, both the Blood Dragons and the GC fight to replace the existing government. One with a true Emperor, and the other with a matriarch.
Rheinland is overflowing with political revolutionaries and every other kind of opposition under the sun, and Bretonia operates in a monarchy. With that in mind citizens in Bretonia as a whole don't want their system of government to change too drastically, they like it, it works. And beyond that, it gives them a sense of national pride.
Liberty really is the only house lacking a proper political movement bent on radical change and redistribution of power.