I think you misunderstand what the government debt is. In simple terms, its people's savings. If the government defaults, it is breaking a contract with its own people. Now we both know this happens all the time in poor countries but its not necessarily a wise route unless you want the US to become a poor country too.
I live in a poor country, the Philippines, but we've never defaulted on our debt. Most of our debt though is to foreign lenders. We were under the Marcos dictatorship for decades and have a lot of bloated crony bank accounts filled with public money, as well as a lot of white elephants (we have a nuclear power plant which was never used but that the government still dutifully paid billions of dollars for), to show for it.
When democracy was reestablished by a peaceful revolution (
http://en.wikipedia.org/wiki/EDSA_Revolution_of_1986) our creditors gave the new government the option to write off our debts since most of the funds lent to Marcos went to him personally (and were used by him for his personal gain) and not the nation. The government refused though and said
the Philippines will pay as, despite how the loans were misused, they were still taken out in the name of the Republic of the Philippines. The name and reputation of the country were on the line and if the government contracted a loan then there was no ifs or buts about it, we would pay.
This debt burden caused a lot of economic hardship and still does. Even now, the proposed national budget for 2012 has debt payments at around 20% of the entire budget. Still, we pay, and continue to pay, because it is the name of our country at stake. We may be poor but we are not thieves who promise to pay and then don't.
I'm not arguing with the point that poor countries are more likely to default, that's a fact. There are some poor countries though who will endure great sacrifice in order to meet obligations they contracted, to prove that they are not beggars who receive handouts but upright citizens of the world community who receive loans and pay back those loans.
It's fashionable now for citizens of rich countries, Greece, America, Italy, ad infinitum, to complain that they should just forget about the nation's public debt because they personally have not benefited from it. When I see these scenes I can't help but think what they are afraid of is not penury but sacrifice. The average citizen of the first world enjoys an immensely comfortable lifestyle compared to those in the developing world. You have benefited from it, in advanced forms of social policy like social nets (ie. entitlements) and reinforcement of the rule of law, to very basic things like being assured that your roads won't devolve into a moonscape of potholes after a strong rain.
Now that the bill has come in for all this largesse, citizens of rich countries just want to wash their hands of the whole mess and walk away?