Three family situations, plus one budget reality.
Minor children. The classic case, and courts say so directly: Alaska's self-help center calls a trust especially important if you want to leave property to minor children.[2] Without one, state law decides who manages money left to a child. Under the Uniform Transfers to Minors Act, which most states have adopted, a custodian manages the property and the child takes full control at an age the state sets.[12]
A trust in your will lets you set the schedule instead: one family pot trust or separate shares for each child, with distributions staged at ages you choose, a third at 25, 30, and 35 in the Washington bar's example.[3] The guardian you name raises the children; the trustee manages the money.
They can be the same person or two different people, and naming both is the will's job.
A beneficiary who shouldn't get a lump sum. Spendthrift terms restrict the beneficiary's ability to access or control the trust principal, and they keep the beneficiary from selling or giving away their interest.[4] While assets stay in the trust, they can also be protected from creditors' claims.[3] If the person you're providing for has debt, an addiction, a lawsuit, or a pattern with money, the trust pays out on your schedule.
Blended families. Leave everything outright to your spouse and the property is theirs, including the decision of where it goes when they die. Trust terms can hold the property instead: income to your spouse for life, principal preserved, and what remains passes to your children from your first marriage. The terms of a trust in your will can be customized to reflect your wishes.[3]
The budget reality. You need a will anyway, and trust provisions add modestly to its price.[13] That buys your kids trust protection without a $1,500 to $4,000 living trust package today.[15] The honest trade: your family pays more later, in probate costs and years of administration. And if your main goal is keeping your estate out of probate court, this tool can't do it.[2]