With small estates, probate is not necessarily an onerous exercise. Some small estates will not be charged any fees by the state. Many states try to make this as simplistic as possible. While a will can set up the trusts used in basic estate planning, the assets normally have to go through probate. Additionally the costs for the attorneys and administrators can be prohibitive.
Estate tax is based on a NET estate.
That is not to say the utilization of a trust is without cost once someone dies since an attorney and accountant will need to be hired anyway. There are several other widely promoted issues for trusts. Probate with a will effectively allows anyone to see what you have done. A trust prohibits the nosey and uninvited from knowing what was done and why. Another issue for many baby boomers is that they may own assets in different states.