There are enough issues to deal with after you die without being left a giant tax mess or a legal battle over your estate. But this often happens to widows and widowers whose spouses have died before cashing in their pensions.
In particular, dealing with a 401k settlement could be stressful and complicated for your spouse or would be beneficiaries upon your death if clear directives were not put in place.
If your spouse or beneficiaries find themselves in this situation then they will be forced to seek competent legal counsel to remedy this complex situation.
Obviously, this will require a substantial cost in attorney fees and will cut into the money they will end up receiving from your 401k account after your death.