If people are really interested in knowing why doctors keep patients alive there is an answer to that one. In every critically /terminally ill patient a point comes where the patient's life cannot be salvaged. But most of the times they are kept alive because of the near and dear ones of the patient. Because doctors have given up and they know they can't do anything more but it is for the satisfaction of the patients relatives till they get the feeling that they have done everything they can the doctors have to go on.
There is nothing more they can do for the patient and the least they can do is give the relatives the satisfaction of having done their best to their loved ones.
It is not really easy for the doctors to go on and show same amount of dedication and more importantly invest in emotions even after the cause has been lost.It takes toll on them but they do it for the loved ones of the patient.
Someone told me that he gets equally touched when he gets a seasons greeting card from the relative of a deceased patient just as he feels touched when he gets from a patient who got cured and doing well.