What you mean is that a lot has been written about spirits. But real evidence? I think not. There may be of course, I have never heard of it. In all my seventy-eight years I have never met, or been in contact with, a spirit. Nor a demon, angel, fairy, or elf. But that does not mean they do not exist. Just that I have never met them. Or mermaids, werewolves,vampires, or dragons.
However, I have often sat in the graveyard where my ancestors are buried, and felt "close" to them.