If someone dies without having left a Will, they are said to die intestate. The consequence of this is that everything they own, all their property, investments and savings, will pass to their relatives in an order of priority which is specified in the Administration of Estates Act 1925 and very possibly this is not what the deceased would have wanted at all.
For example, if a married man with children (no matter how old they are) dies intestate, and he leaves more than £322,000 then his widow will have to share part of the Estate with their children. This might be entirely impractical, especially if the estate includes the matrimonial home or a business. It does not take very much time or effort to make a Will, and it is reasonably inexpensive, and by making a Will you can make sure that your affairs are dealt with as you would want them to be dealt with and you will be minimising the upset and distress to your loved ones. It can of course be difficult to consider your own mortality, but making a Will never killed anybody.