Culture Colonies?

As powerful as culture is in the late game, it doesn't seem to make much of a push, particularly with a colony ship in orbit. The planet may be lost repeatedly due to culture failure, but they can recolonize till cap ships arrive to push away enemy culture. I think culture might be more useful, in early and late game, if it would actually colonize the planet's that the culture overthrows, including neutrals. I'm just not sure if that's even possible in the game. The idea is that while one focusses on specific tasks, culture can spread to local worlds, perhaps world's with strong militias, and capture the planet and convert a percentage of the orbitting fleet (if neutral, if owned by another planet it could only take control of stations). It seems to make more sense than just turning enemy planets into neutral ones, and just passing through neutral ones. Is the message being sent by each empire just "ANARCHY" or something similar that the people don't unify with the overpowering culture? The last bit is more of a plot hole than a real question