If you're talking about Feudalism, it's in there for the civ that is in the early Middle Ages, has a number of small towns, and needs an army to expand. Germany in my current game is a perfect example. 11 towns, with the largest size 5. Germany has a huge army, and just finished taking out England. With any other government, they'd be bankrupt, but because they are in Feudalism, they can support an army of the size they need to expand. They'll probably switch over to Monarchy soon, but for now, Feudalism is doing them a lot of good.