Bigotry, donor fatigue, bigotry, the slow-motion nature of flood disasters, and ...ah...bigotry.
At this embarrassingly late date, NPR should really be less ingenuous in its reporting on these matters. It is not one world, and people are not all the same except for headgear and cuisine. Why are Westerners reluctant to donate to Pakistan? Because the Taliban has been carrying out its threats to murder Western aid workers, even during this disaster. And because there is a high likelihood that the money and aid donated will be siphoned off to corrupt officials or worse to the Taliban itself, to be used against our soldiers. And because Islamic charities are not like Western ones, in that the Islamic conception of "zakat" includes conventional charitable aid, but also bribery and funding of jihad.
The poor wretches... One can only hope that a lot of al-Qaeda have drowned also, up there in the Swat Valley.