Each state's scheme differs. Even if you would distribute your assets in the same fashion, the probate court will get involved, which can delay matters and add unnecessary costs. All told, it makes no sense to encounter complications and lose control over your own property. It delineates what type of life-sustaining measures you want to receive if you are incapable of making your own medical decisions, and it designates who should carry out your wishes. Without it, you cede control over these very personal issues to other people.
Many states provide standardized forms that are free.
You just fill in the blanks. If your estate is sizeable, consider a revocable trust. A will is a public document while a revocable trust is not. If you fund your trust while you are alive, you also make it very difficult for heirs to contest the trust's provisions. Another common estate planning error is failing to name a beneficiary on your retirement accounts.