Yah in most cases 2x200 is the step up from 200. The reason being is your wire that runs your 200A service isn't big enough to carry 400A, so you would need to tear it out. Why tear it out a perfectly good wire when you can just run another?

My house is a really big house built in the 50s. It was initially 2x100A service as I don't think 200A service at home was really a thing. It had 2 meters and everything. Sometime in the 80s they tore out the feed from the pole and put in a proper single 200A line, and just left the second meter as defunct.