I'll be dead. I won't exist. Therefore it won't be possible for me to care. But let's not just limit this reasoning to atheists like me. Let's say that heaven and hell also exist. Just for the sake of argument. If you go to heaven, you'll have better things to do then to worry about what happened to your mortal body. And if you go to hell, you'll have bigger problems to worry about. Or if you're reincarnated, you won't know and therefore you won't care. It doesn't matter what kind of afterlife you believe in, what ultimately happens to your body will never in any case be any of your concern once you're dead. Unless terms of accessing certain afterlife demand a proper burial or something like that. But since you can never know that for sure, you might as well just forget about it. What's the point of worrying about this now when you're alive? So you see, it doesn't matter. You shouldn't care. Let people you leave behind figure it out.