I think it's because the more we learn about the universe in which we exist, the more and more apparent it becomes that we are not a special part of it, that th

I think it's because the more we learn about the universe in which we exist, the more and more apparent it becomes that we are not a special part of it, that there is so much more to it than tiny slice of space and time we happen to occupy. The universe existed long before us, and it will continue long after us. We are inconsequential. This is all pretty contrary to what most religions tell us. Personally I have no reason to trust or believe what clergy say (they're as human as the rest of us and make lots of unverifiable claims), so all I have to go one is what we collectively discover about our universe.