First, there is a principle called fiscal anesthetics that basically says that governments should tax people when their resistance to taxation is at their lowest point like, for instance, when people are happy because they are about to receive a big inheritance.
Second, an inheritance tax is the way to have a redistribution of income. People think that what they amassed during their life time is simply the fruit of their hard work, but that may just be true in part. The other part according to Marx comes from the redistribution of the surplus taken away from the workers by the capitalist class. For instance, there are lots of people that I know that have paid peanuts for their homes that are now valued well above the 1 million dollars mark, with some of them receiving the full pension, implying that taxpayers are paying for their retirement so that their children can inherited a tax free home.
Third, there is nothing, besides politics, to stop governments from taxing capital distributions and implied income derived from the usefruit (usage or benefit) of property kept under trust. For instance, if A is living in a property being kept in trust for B then B should be said to be receiving taxable income from the trust at the ongoing rates for rental accommodation in the area.
