This thought raises the question of the sanctity or value of human life.
Think of how many times people have been told that they may not survive 6months and they end up living for 5yrs more...
Or the times where someone who was terminal suddenly went into remission with no plausible explanation... What would happen if the individual decided to end his or life earlier because of pain it torture the individual experienced?
It is a dicey subject matter.
If someone is suffering a lot of pain and he or she wants to die to end with that suffering, they has the right to decide it and doctors has to be legally able to help them. You're a doctor and you know that those cases you say doesn't happen very often, in reality it's quite the opposite.