The system of Civil Registration, introduced on 1^st July 1837 is a fantastic research tool for family historians.  Its introduction was controversial at the time.  Previously all births, marriages and deaths were entered in church or chapel registers as baptisms, marriages and burials.  The new regime reduced the power of the religious bodies and resulted in an immediate fall in the number of baptisms.

The absence of a date of death is a frequent feature of many family trees.  To me the date of demise of a relative completes the story of an individual and shows you have attempted to trace their whole life.  It can also throw up some information that you will not find elsewhere relating to their life and your family.