AFAIK, (and I'm a pretty ignorant fellow) debt in America isn't passed down, the creditors just take what they're owed out of a dead person's estate before its divied up by a will. So there could be a big "pop" if a bunch of people with lots of student loan debt and no assets die.
You mean the estate that contains value I would otherwise get the full value of were it not for the student loan debt that was taken out? The debt is most certainly passed down, it's just abstracted away a bit. The only way the debt doesn't get passed down is if the debtor dies penniless.
Another way to put it is if the creditor extracts anything to pay that debt after the debtor dies, then the debt is most certainly passed on to someone because that money didn't materialize out of nowhere.