As I'm sure at least some of you saw some months ago, Lamar Odom (former NBA star and husband of Khloe Karsashian) went through a medical emergency that prevented him from making his own decisions. This is a good way to illustrate the purpose of estate planning and why it's a good idea to re-assess your estate plan when you're going through a divorce.
When you become incapacitated in a medical emergency, if you have a healthcare power of attorney it will become effective. Your healthcare agent will be able to make medical decisions for you that your are currently unable to make for yourself. If your condition worsens and you're ultimately facing imminent death or a persistent vegetative state, your living will (or advance directives) will become effective.
When Lamar Odom was incapacitated, he did not have those two documents in place so, his soon-to-be ex-wife (still legally married) became his agent by virtue of the laws in place in that state. Ask yourself this question: If I were getting a divorce, would I really want my soon-to-be ex making life-or-death decisions on my behalf? Didn't think so. In the absence of a will or living trust, Khloe stood to inherit the lion's share of his estate through intestacy - probably not Lamar's intent, especially with Lamar having children from a previous relationship that depend on him.
Luckily for Lamar, Khloe took the role seriously and things went as well as possible for him. Main point: divorce changes a lot of things, but you have to take it upon yourself to make the important estate planning decisions during and after a divorce. You can't just hope for the best and that your ex will do what's right. Sometimes, they won't.