If you’ve researched your family history for some time or had a semi-serious interest in it for a while it is easy to forget that others do not.
If you’ve been involved with research for a while, you could probably easily (with some exceptions) give complete information for the death certificate for most close relatives. But you are not typical. Your knowledge is based upon interest you may not share with others and your own research. Your cousin who gives information on a death certificate in 1930 when her mother dies does not remember all that information–if they ever even knew it.
Sometimes when we’ve known information for years it can be easy to forget that others simply do not know and to assume that everyone knows what we do.