Families not only pay for obituaries, but also write them. This development has been good and bad. Mostly bad, in my opinion. Many obituaries these days don't provide some of the basic information sought by genealogists. Often, vital information is missing, either because nonjournalists don't know the essentials of a good obituary or because the family couldn't afford to publish all the information that should be included.
Cost is no insignificant consideration.
At an average of five to six words per line, costs add up quickly. I don't know who writes obituaries in most families these days, but I suspect the family genealogist is a likely candidate. Date of death, including day, month and year. Often, relatives clip an obituary from the paper and save it without writing the date of publication, or even the name of the newspaper, on it. This can leave the death date a complete mystery to future family researchers.