When a system is set up to accomplish some goal, a new entity has come into being — the system itself. No matter what the “goal” of the system, it immediately begins to exhibit system behavior; that is, to act according to the general laws that govern the operation of all systems. Now the system itself has to be dealt with. Whereas before, there was only the problem — such as warfare between nations, or garbage collection — there is now an additional universe of problems associated with the functioning or merely the presence of the new system.
Put another way: When faced with a problem, you might try building some sort of system to address that problem.