I originally started this as a comment, but thought it deserved a place in the sun.
Anon, I don't take your questions as confrontational. They're perfectly reasonable. I don't believe my grandmother's spirit is anywhere. I believe we live and die and that's it. There is no scientific evidence for an afterlife or a god and so I stick with what can be proven scientifically. I was led to this belief over the course of time by a few things. First was the hypocrisy I saw in people who claimed to be "religious." People claimed to believe in what Jesus taught and then didn't even come close to following it. And that seemed rampant and so I at least rejected organized religion. Second, as I tried different religious sects, I realized that I did not believe that it was even possible for the events and people in the Bible to have the kind of power over our lives that almost every religion I've encountered believes is the case. As I thought about it, I came to equate those religions with the Greek and Roman gods. They were myths and maybe they were helpful for some believe in figuring out what life is all about but they certainly weren't for me.
When my sister died, a common thing people said to me was "It's God's will." If it's God's will to let a 17 year old girl die, then I want no part of it. I think if we can displace our responsibility to each other as humans onto a spiritual being, then we become immune to the needs of others. We start to think that it's God's will for some people to be poor and sick and not our responsibility to make sure that people have opportunities and are taken care of. If we believe that there is an afterlife, we may take the here and now for granted.
Would I like for there to be an afterlife? Sure. It's be great to think that we can go somewhere after we die and be with people we love. I understand the comfort of that belief. I don't want this life to end, but in accepting that it does, I am obligated to make it the best life possible, not just for myself, but for the people I'm sharing that life with--and that includes people I'm just sharing the earth with.