Very simply, because it makes it easier for those that you leave behind – your loved ones.
When you die, everything that you own (money, property, possessions etc) needs to be passed on and making a Will, makes sure that it goes exactly where you want it to.
No Will means the Intestacy laws will determine who’s going to get what (and that might not go where you want it to go to).
Not only that, but there are legal requirements that need to be actioned after you’ve passed on and a Will allows you to nominate who should handle your affairs. So even if your estate is relatively small, it’s still helpful for your nominated person to have the legal authority to be able to quickly get on with sorting everything out.