I’m a long time nurse. It has been my experience that you are right about this at least some of the time. Sometimes people are surprisingly ready to die however and they truly don’t want any “heroic measures”. I guarantee you that I don’t ever look for an excuse to let someone die but many doctors are quick to walk into the room with a blank DNR form and they can be pushy about it. It’s best to figure it all out before you get to the ER and find yourself unable to communicate your wishes, have it all in writing and on file with your usual hospital.
I deal with this constantly at this point. Fortunately my Dads regular physician completely understands my concerns but everytime he’s hospitalized I get tremendous attention from physicians chasing me with DNR forms.
Most people think of extraordinary measures as CPR or a heart/lung machine but it can be less than that.
I don’t consider IV fluids an extraordinary measure but I personally know someone who died because she was comatose and fluids were withheld because of a DNR.