One quirk of the laws in my country is that you can’t have arbitrary wills. Your family will inherit your possessions, and the order in which their claims have priority is also established. A will helps that process go more smoothly, that’s all.
The only guaranteed way to make sure your estate goes where you want it, is to enact the transfer when you’re still alive. Which has the added benefit of allowing you to see the impact it makes, so maybe this is a good idea in other places too.