Probate is a public affair. Because the will or estate goes through the court system, the information that arises is a matter of public record. While this may not be a major concern for some people, others prefer to keep matters of money, property, and inheritance private.
Those who only have a will and those who have not planned their estates at all will have their assets go into probate. But those with assets in a living trust will avoid the whole probate process so that their assets can be handed down quickly, efficiently, and privately.