Read a piece on Salon that gets right down to it about the Tea Party Repubs in the House. (Sorry for the awful ads on Salon.)
They don't worry about re-election because they come from solidly Republican districts, and won their seats in primaries, not in the general election. The voters in their districts agree with their belief that a default would be a good thing for the US, would help us bring our fiscal house in order.
So when the Republican leadership, who are thinking about things like winning the Presidency or the Senate, or even holding onto the House next year, press them on the risks they're taking on behalf of the party, they don't care. Their seats are safe, they reason.
But they might want to think again. Seriously. If there was an economic collapse, maybe the voters back home might change their minds about whether defaulting was such a great idea. Voters have a way of punishing reps even if they agreed with them, if they turned out to be wrong.
Also, even if they get re-elected -- what exactly will they get re-elected to? We live so high, we have a long way to fall. They might have other problems to worry about, like feeding their families. I can't imagine the govt will be very anxious to pay their salaries. Wouldn't it be something if they expected to get paid even if the US defaults? (Hey I bet they do expect to get paid. Someone should tell them that's not how it works. Might change a few votes.)
And btw, if you're worried about the government's deficit, corporations are borrowing much more heavily, and are even more leveraged than before the big collapse of 2008, and more concentrated. Even without the US govt defaulting, we're headed for another round of too-big-to-fail failures. If you're tired of this stuff, there's a lot more to come. :-(