Fred Wilson Warren, My Grandfather-

Fred Wilson Warren
Born August 1, 1906 in Maryland, and died October 1975. Fred's parents were (supposedly) Charles Warren of Virginia and Eva Diggs. As the family story goes... Fred's mother Eva died in the influenza epidemia around 1917/1918. His father had at least one other child, a daughter, and couldn't care for the both of them. He placed young Fred in an orphanage, from which Fred ran away. The 1920 census shows him, as a boarder, living with a non-related family in Baltimore. He was 13 years old.
To date I have been unsuccessfull in finding Fred's parents in the 1900 census, or any of the family in the 1910 census.
Why is it, by the time we're old enough to ask questions about 'things,' the people we need to ask have passed away?