There is some evidence that Americans will schedule their deaths in order to save on taxes (http://www.columbia.edu/~wk2110/bin/dying-final.pdf). I wouldn't be surprised if the cultural equivalent is scheduling one's death to give your loved ones more vacation time...
As the paper mentions, it's also possible that people are lying to the IRS about the date of relatives' deaths. (I personally think that's the more likely interpretation, but I guess it depends on your priors).
