Let's ask a different question: why do the rich have the obligation to bail us out when our politicians spend recklessly?
Since the New Deal, politicians from both parties have used deficit spending to fund the programs that generate political support from their chosen constituencies. Rather than spending based on the total annual tax revenues (or even projected revenues), our "leaders" in DC decide what they want to spend first and then look at how much we'll have to borrow to make it happen. Of course, the realization of how much we must borrow does not slow down their spending plans.
Because the "rich," from one perspective, "can afford to pay a little more," we expect them to serve as the coffer for us to draw from when we are out of ideas. Rather than completely reform federal spending into a manageable and balanced approach, the politicians choose a minority of Americans that are easy to demonize with the rest of Americans ... the "rich" (of whom most politicians are members).
I understand that they are able to pay higher taxes, but the question we should be asking is this: even if the rich pay higher taxes, what will change with the way government spends our money? I don't see the rich as having the obligation to bail out politicians who manage money poorly. It's a convenient and romantic notion to suggest they should, but according to the Constitution, they shouldn't. Every citizen should have dual representation under the law, and that includes the Federal Tax Code. The "rich" already pay 80% of the federal taxes collected in a year. By that standard, they are already paying more than their "fair share." They don't have an obligation to pay more just because we want them to take our burden from us.