The Medicare Hospice benefit requires physicians to certify that the patient has only six months to live. This is of course impossible to predict accurately (and only the government would come up with something so stupid.) Many patients  get into hospice much later than might have been of benefit to them (and their family.) The GAO report from Sept. 2000, noted that in the 90's the average length of stay fell 20% from 74 days in 1992 to only 59 days in 1998. The government has responded to this by persecuting programs that have patients who "live too long" (since 10% of the patients live longer than 6 months.) It is useful for doctors to at least have some idea of average prognoses which is the purpose of the tables listed above.