Into kingdoms, which also failed. Most Western countries have some form of democracy, which replaced the kingdoms, as the chief hobby of kings was war, which was very unhealthy to the nobility especially, but also the general citizens.

Socialism developed as a side project of a man interested in starving his family and convincing the world that he had an original idea: someone else owes you a living and you can demand that they provide it. Corollary: rules are for other people. Violence and strongarm state tactics may be necessary to produce socialist utopia. That failed too, every time it was tried.

The first obligation of any government is to protect the lives and property of its citizens. Everything after that can only be accomplished after the first duty is fulfilled. These city-states could not do that. Therefore they will never be.

One could make the arguement that it evolved into the current financial state and system we live in today.

As a gebur in Anglo-Saxon England you'd be expected to pay a set amount of food rent to your thegn or ealdorman who served the king. They in turn would provide services to the king either through membership of his welrod or later fyrd or through other means, economic or otherwise.
Now, when you pay your taxes...who do they go to? Local government, and then through various financial levies all the way up to national government. From the gebur (you) to the king (US government).

Politically the system changed, but financially, it stayed fairly similar. The primary difference is in how much is levied by the thegns, and now we use money instead of food rent.

I would also add to prevent their oppression as well, be it through enemies foreign or domestic.