Use of Time Travel

In this chapter Billy Pilgrim reveals the way he will die to the reader. He knows of his own death because he has lived through it already. I find Billy's approach to time travel very peculiar. At times he uses it to avoid enduring bad times or while he sleeps. But he doesn't try to change his fate. I remember in Harry Potter and the Prisoner of Azkaban Hermione uses her time-turner to go back in time and save Sirius Black and the Hippogriff. If time travel was truly real, my expectation would be that everyone would try to avoid death especially being assassinated. But Billy Pilgrim is a unique character who simply accepts his fate and kinda shrugs it off.