There was an article recently agreeing with this point--that a mix of fear, selfishness, and guilt imposed by family and friends motivates many to "keep fighting," when they had previously and privately (away from loved ones) expressed their wish to die.
IIRC, the doctor in the article discussed how awful she felt at witnessing and being part of these prolonged treatments.
Can't find it now, but this seems to be a topic with a long history on NYT: