Because it's the only way to take proper care of the elderly and the disabled. No anarcho-syndicalist pipe dream has ever convincingly sketched me a scenario where the elderly (without family) do not just waste away in isolation, and the schizophrenics are rotting in the streets.
Now, a government is not a guarantee to fix this (see for example the NYC homeless), but without a government, the weaker groups in society are just shit out of luck.
Block Island, RI, is a good example of a community thant functions to help each other without government aid. http://www.youtube.com/watch?v=SUxu02GPAqg
And government has been similarly horrible at taking care of the poor. a large part of social equalization in the 1900-1950 era was the ascendancy of private community associations, mutual benefit societies, and so forth. The remnants of these are the Kiwanis, Lions, Rotary club, etc... But these have been squeezed out by government sponsored programs, and we have seen economic inequity rise. Part of this is probably also because the poor have been squeezed by money printing - but that's another issue altogether.
Especially the way that the government engages in charity. By spending money that is borrowed to bail out the poor (the anti-austerity argument) - the government transfers funds to the poor (which, let's assume is fine) by borrowing from the rich and politically connected. But it's a loan, so the rich are getting paid back, with interest. The net resource flow is to the rich, even though you have paid the poor.
Sure, the kids may clean their room if you tell them they can have cookies afterwards, but what's the plan when the anarchists have already achieved their goal and removed that external motivator?
And that is assuming people are completely irresponsible and don't save during their lifetime. Pensions is just that, but with a middleman.
Or if you like
"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."
The moment that you abolish government I will personally get a gang together to make you regret the action. The power vacuum will be filled, and given the opportunity I would much rather be the one wearing the boots than the one getting his face kicked in.
I like to think that most libertarians are mostly confused anarchists, and thus mostly imbeciles, but those that can deny the necessity of government altogether are beyond idiocy into an entirely separate plane of existence. It's beyond even opprobrium; we simply do not live in a world that would permit large groups of humanity to live without some form of government.
A government is a local monopoly on the use of force. We do not live in a world that can be made free of violence, therefore government is an unpleasant necessity. Solve the violence issue, and we can talk about abolishing government -- although you should also be aware of the concepts of "market failure" and "natural monopoly".
But, you can be forgiven for forgetting that fact. It's really hard to remember these days.
Still, for the record, we should all be suspicious of anyone who seeks to disempower the government in a country wherein self-rule is supposed to be the law. There is a third option, and that is restoring the spirit of our government.
http://www.eleuthera.it/files/materiali/David_Graeber_Fragme...
Edit: And to avoid might makes right?
That is of course assuming we do not end up with the same M&A activity that leaves only a handful of law market/arbitration agencies (similar to what has happened in many arenas, such as media).
I am going to have to think about that one for awhile...
Because I don't live in a spaceship with nuclear power, an FTL drive and a working replicator to run away from the rest of humanity.
See Sethrin's comment.
