Generally, we all tend to not believe in what we can't see. Of course, this carries over to believing in God and the miraculous. Many will say it's not logical or rational to do so. And yet, we believe many things exist that are invisible to the naked eye and miraculous in nature—thoughts, atoms, and even feelings of love.
The reason it's not logical to believe in God is that it doesn't fit what we know in the natural world. This is our human dilemma. God is supernatural—He's above and beyond the natural realm. He will never fit within our limited logic. God's existence exceeds our capacity to know Him in a purely natural way.