Estate planning isn't a particularly pleasant experience, which might explain why so many people put off doing it until it is far too late. Other people will create a basic last will but won't go through the comprehensive process of planning their estate.
You probably don't just want to decide who gets what for after you die. You may also want to have protections in place in the event that you experience medical incapacitation to help protect you and guide your loved ones. Even if all you wanted is to allocate certain assets to specific people, you will want to execute beneficiary designations for existing accounts.