No one really wants to think about what will happen when they die. However, if you do not plan ahead and make a Will, then the laws of intestacy will apply. You will also leave an Intestate estate if you do not update your Will after getting married (unless your Will specifically states it was made in contemplation of that particular marriage).
When a person dies without leaving a Will, this is called dying intestate. Instead of an executor applying for probate of your Will, a close family member may need to apply to administer your estate and your assets will be distributed in accordance with whatever law applies to intestate estates as at the date of your death.
Even if you are happy to leave the distribution of your estate to whatever intestacy laws may happen to apply as at the date of your death, you need to think about the added costs and burdens this places on the administrator.