Inheritance tax is usually only on values above a certain point, though. That point can easily be set reasonable high – say, 5% tax on all inheritance above €2M, and 40% on all inheritance above €10M, and normal families would hardly be affected.
In theory, it is nice; however, valuing assets is not easy, especially for the whole population. This arbitrariness clashes with the principle of equal rights in most constitutions.
On the other hand, taxing income is very easy since the number has a precise origin.