Why are governments set up?
I wrote governments are set up to secure the rights of people. Is. This right answer
Originally, governments were set up so the people forming them would have protection from other people -- and notice two particular passages in the US Constitution:
1. In the preamble: We the people of the United States, in order to form a more perfect union, establish justice, insure domestic tranquility, provide for the common defense, promote the general welfare, and secure the blessings of liberty to ourselves and our posterity, do ordain and establish this Constitution for the United States of America.
2. In Article II Section 2: http://www.law.cornell.edu/constitution/articleii#section2
The president's most important jobs are listed first. That's not to say the others are unimportant, but that his first responsibilities involve keeping the US safe from harm, from outside or inside.
John Locke and Thomas Hobbes have expressed it all pretty well, although not everyone has agreed with them over time!
Thomas Hobbes famously said that in a "state of nature" human life would be "solitary, poor, nasty, brutish, and short". In the absence of political order and law, everyone would have unlimited natural freedoms, including the "right to all things" and thus the freedom to plunder, rape, and murder; there would be an endless "war of all against all" (bellum omnium contra omnes). To avoid this, free men contract with each other to establish political community i.e. civil society through a social contract in which they all gain security in return for subjecting themselves to an absolute Sovereign, preferably (for Hobbes) a monarch. Though the Sovereign's edicts may well be arbitrary and tyrannical, Hobbes saw absolute government as the only alternative as the terrifying anarchy of the state of nature. Alternatively, John Locke and Jean-Jacques Rousseau, have argued that we gain civil rights in return for accepting the obligation to respect and defend the rights of others, giving up some freedoms to do so. The central assertion of social contract approaches is that law and political order are not natural, but are instead human creations. The social contract and the political order it creates are simply the means towards an end — the benefit of the individuals involved — and legitimate only to the extent that they fulfil their part of the agreement. According to Hobbes, for whom government is not a party to the original contract, citizens are not obligated to submit to the government when it is too weak to act effectively to suppress factionalism and civil unrest. For other social contract theorists, citizens can withdraw their obligation to obey or change the leadership, through elections or other means including, if necessary, violence, when the government fails to secure their natural rights (Locke) or meet the general interest ("general will" in Rousseau, who is more concerned with forming new governments than in overthrowing old ones).