Wills
Wills are a guarantee of probate. Then why have a will?
Wills work fine in a couple of circumstances. If you don't own real estate and your assets are under $100,000, then you do not need a trust. $100,000 is the probate threshold in California. Probate fees on the first hundred thousand is 8%, or $8,000. So, for small estates, wills are fine. Wills are also fine for estates over $100,000 if you don't care much about the beneficiaries, and don't really care if they have to go through probate after you die.
Sometimes, especially with families just getting started, there's not much in terms of hard assets (renting - not owning - and not much in terms of investments and savings outside of tax-deferred accounts) but a ton of life insurance (usually term). Well, you don't need a trust, because you're under a $100,000 in hard assets. But with minor children you need sub-trusts for your minor children in the will because of all the potential life insurance death benefits. These are what are called complex wills. This way you can name Uncle Wally to manage these potentially considerable insurance assets for his nieces and nephews (children of Wally's brother and brother's wife) in a catastrophic scenario for the brother and sister-in-law. This will won't avoid probate. But if there will not be a probate, and we need sub-trusts for minor children for potentially large insurance proceeds, a complex will is the ticket.