I think people see their lives as stories, and they want their story to have a happy ending. Death kind of puts a damper on that. Very rarely does someone die having lived a full enough life that they have accomplished enough to satisfy them, have loved and been loved enough to feel secure, and do not have any unfinished business. Death ends their story before they feel it's finished. It's not the prospect of what happens at death that makes people uneasy or afraid; it's the prospect of losing all they have here.
I agree with your point to some extent. We all want the happy ending indeed

and we sure don't want to lose a thing we own, but we usually don't really know when we'll die so we don't feel like we've been cut short, others do for us. We're dead, we didn't see anything...Except in some cases where your idea applies perfectly (terminally ill, death sentences)
Imagine what life would be like if we possessed our birth and death certificate "from birth"? We would live in a hectic constant rush to "finish" things, I think we'd go crazy. But then again, would we even have the same opinion on death if it was given to us from birth? Would our attitude towards limits in general change?
Some view death as a way of freeing themselves from pain, no matter what there is after death.(ex: a christian commiting suicide would go to hell, boy wouldn't that suck? and what about someone who believes in reincarnation how would they see it?Just a cycle?)
People who commit suicide are selfish in our eyes, we are in theirs because we are preventing them from their "ultimate relief" to their pain if you will.(I mean the "natural" thing to do is try and live when you go backwards you have a mental problem in my opinion...>.> Are there other living beings that purposely go to their deaths from their own choice(excluding dying because you mated)? but then again, just my opinion)Of course they are not thinking about us when they are killing themselves since we suffer the loss, they're dead.
I also completely understand you whatever, surely no one wants to believe that there is a complete end somewhere. As a matter of fact, this belief is widespread I don't know a single part of the world where some sort of continuation after death, reincarnation or not does not exist, even ghosts or spirits etc..We just can't live with that idea of "finality".I guess it's human, I don't think anyone doesn't believe in something like that. Even "legacy" is a sort of after death even if it's not "spiritual" it's like a story is kept alive through the closed ones so that the story isn't forgotten and doesn't die(aka memories being passed on).

We all need to leave a trace in the world to show that we existed, I agree 100% with whatever on that one

, I'm pretty sure the idea of not having some sort of ceremony after someone's death is disturbing to most people for a reason. We need to acknowledge that "bobby was here" in some sort of way and externalize it so it is remembered and doesn't "get lost" by not being transmitted to the outside world.
Now why does the idea of that "stop" sign bother us? I actually don't really know...
I always need (my case and probably a lot of other people's)to feel like I am moving towards something, continuously, as if flowing freely and constantly...towards what?I don't know...But I know I need to keep on moving.
My 2 cents, ^^