Because this is the difference between the Nietzschean and the Christian. For the first, the world is radically open-ended and any human future is a possibility. The Christian would also acknowledge that because humans are no longer fated by the gods and determined by outside forces in the way they were, that a wide range of futures is a possibility, but however it is attained the future has a goal, a telos, an Omega point. And the striving toward that endpoint is what gives meaning and significance to what we do now.
Underlining is my emphasis