To be honest you'll have to ask the writers of the storylines, Del - we can't look into their individual justifications.

I will attempt to suggest something Batman has stated many times - he does not kill because it would be too easy. And actually I think it was Wesley here who said that it was uncharacteristic of Batman to let Ra's Al Ghul die in Batman Begins - Batman tries to stop criminals but if the criminals are going to die, he needs to save them - because that is the right thing to do.

It's very interesting to note that the Non-aggression Principle also advocates this sort of action (that if somebody attacks you and stops, you stop defending yourself, and if the person then is in risk of danger you are obligated to help if possible). Perhaps superheroes follow the NAP?