In the Known Dimension, Imperialism is the most popular form of government. 63% of government entities in the KD are imperialism, or a form of it. Democracy, although stilled used in many absolute monarchies, did not take off as a full form of government, many people believe this the be because many nations and their leaders did not really like it as much as their old forms. Another reason could be that some nations have had imperialism for many eons.
Imperialism is said the be the first form of government in existence in the Known Dimension. It was probably created in the Sumerian Galaxies, the group of 7 galaxies where civilization began. Many other nations afterwards also chose imperialism.