The intent of checks and balances was to prevent any one branch from becoming too powerful. And generally, the government governs best who governs least: and the concept checks and balances also seems to promote that as well. The problem is this, however, the legislature being an often fractious due to its bicameral nature, often does not have the wherewithall to really stand up to the executive or judicial branches. While the judicial also has a mixed court in the SCOTUS, they generally are not challenged by any of the other two branches. And finally the Executive, which has broad regulatory powers either given by congress or simply seized through precedent, is often not sufficiently checked by congress OR the judicial. So the system isn't perfect, but then, no system is.