One advantage is that it can help you better understand the overall plot development. For example, if it's a mystery story, knowing the end might make you notice the subtle clues that were planted throughout the story more easily. It also allows you to focus on how the characters are leading up to that end point, like their actions and decisions that are in line with the final outcome.
Knowing the end in advance can be great for a reread. You can pick up on things you missed the first time around, like foreshadowing. It also enables you to have a more relaxed reading, especially if the story is really intense. You can just enjoy the journey of how the characters reach the ending that you already know.
Well, it gives you a sense of security. You don't have to be on the edge of your seat worrying about what's going to happen. And it can be a different kind of reading experience. You can analyze how the writer is building up to the known ending, like looking at the pacing and the way the story is structured.