I think you're missing the point, gaelic.
Would I have believed in atoms a couple of hundred years ago? No, I wouldn't. And I would have been right not to do so. It is entirely illogical to believe in anything without justification - even if that thing much later turns out to be true. We either have solid reasons for what we believe, or we don't.
(Incidentally, atoms is a very bad example here. The history of their discovery goes back much further than a couple of hundred years - but I'll go with your analogy anyway).
You are confusing possibility with probability. Any scientist will tell you that, of course, it's possible that we survive death in some way - the question is whether, on current evidence, it's probable. And the answer to that is, no, it is not. It's is exceedingly improbable.
This isn't just because there's no evidence demonstrating it, but because all the evidence we do have (which is pretty massive) strongly, strongly indicates that death = the end of experience. Not quite the end of existence (depends on how we define existence), because our atoms will continue, and we are, after all, a walking pile of atoms - but our experience of "being" will almost certainly end.
While there's no solid understanding of what consciousness actually is, it's pretty well understood that it's an emergent property of brain matter. When brain matter has rotted into nothingness, how will consciousness continue? My voice is an emergent property of my vocal cords. When they are gone, what happens to my voice? It no longer exists. Thoughts and experience almost certainly go the same way when the brain goes.
Believing in life after death without good reason is, by definition, an unreasonable belief. And there is never any justification for holding an unreasonable belief.
If I find, after I'm dead, that I am somehow able to come back and spook my grandkids then that wouldn't mean that I was wrong not to believe this was a possibility while I was alive. Since I have no reason to believe that now, it would be unreasonable for me to do that.