This is a really bizarre way of looking at things, because it basically denies the possibility of investing in any characters in any work of art who don't die. There are always some "safe" characters and always some "unsafe" characters, because there will always be some characters that need to survive to the end of the story. Does the fact that Fortinbras survives The Tragedy of Hamlet but Hamlet does not, mean that you won't invest into the Hamlet character? Does it mean that Hamlet's life only matters insofar as how it impacts Fortinbras? And let's accept your premise that we know some characters may die and some may not. Why does that mean that the ones who may die only matter insofar as they impact the ones that may not? Why are you unable to invest into those "unsafe" characters' emotional journeys the same way you would a "safe" character's journey? Why does being "unsafe" render the character's life meaningless? Why do you only apply meaning in terms of their impact on "safe" characters? Why don't the characters just matter to you, period?