Why aren't developed countries saving?

Change of intertemporal preference would not be my first answer. But that is precisely what Dobrescu, Kotlikoff, Motta say in their article (European Economic Review, August 2012), at least for the US:

American and French societies are placing increasing weight on the welfare of those currently alive, particularly contemporaneous older generations. Government spending also appears to be one of the reasons why France is saving at much lower rates.

An early draft is here (2008).