Of course we don't know everything and shouldn't care about everything. However, we have lots of things we care about for good and less good reasons. It's natural and good to care about your friends and family or even your country and maybe the future of humanity. We need to make decisions based on these factors. While we stop being able to influence outcomes, it would IMO be odd to simply not care what happens after.
Sometimes, you don’t know everything, nor will you. You won’t be around for everything. This is the human condition.
It seems unwise to spend too many brain cycles worrying about this.