We look to both negative and positive examples of what we want for information on how to obtain it. In this case we want positive examples of civilizations providing stability and meeting human needs well. Stability is a key parameter which is why we spend so much time looking at long lived civilizations. The Republic of Venice is notable for being extremely long lived, and relatively neglected by people studying history/using historical examples to support political theories. I agree that traditional monarchies don't have a very good base rate of success BTW.