Without being morbid, as some may think it is to read obituaries, such articles can be great resources for family historians. Older newspaper obituaries can provide information about the person's family, place of immigration, dates of major events such as moving to another state, occupation(s), possible military service, burial and other pertinent information. In some cases the obituary can provide a birth date and/or place, which can be helpful when no birth certificate or baptism record exists. Do not be fooled that the obituary or death certificate is a "primary" source for your ancestor's birth date though.
Sometimes there may be no obituary in a local newspaper or it may be a single line listing the person, date of death and possibly another fact. Other times you may need to check Church newsletters for obituaries. The Seventh-Day Adventist Church publishes 'The Pacific Recorder' on the West Coast and it is possible to find obituaries for members of the church in states such as California. For instance an obituary in 'The Pacific Recorder' can provide information pertaining to when your ancestor joined the church and other information similar to newspaper obituaries.
Next time you are researching your family, try locating an obituary, you may be surprised with the information you gather that can lead you to other sources of information. And if you are trying to find living relatives you may be able to find out a relative's living relatives at the time of death and children's married names.