Of course, it's necessary that it be that way, from the writers' perspective. Largely because if the Doctor ever *did* decide that he was done with people dying on him all the time and therefore, well, _fuck death in the general case_, there is a very good chance that he might actually be able to pull it off.

Which leads to the universe becoming very weird, and not in a cute portrayable way for companions and bystanders to boggle at, in rather short order.