The problem with this subject and many people is that in order for them to believe that such paranormal activity happens they have to experience it themselves. Believe me, I think I can speak with more authority than most on this subject.
I really don't know what the whole thing means but I can assure you that if you'd lived in my house for the number of years that I have then you'd certainly have come around to the idea that ghosts, for want of a better term, do exist. The number of things that have happened to my family and friends down the years goes into the many dozens and many of these occurances have been of such a nature that, quite frankly, it seems impossible to come up with a rational explanation for them.
These events go from the simply odd, such as objects moving about, strange noises and various other stereotypical haunting behaviour, right through to the appearance of an apparition (an old lady in a black dress and shawl) and people being grabbed or pushed by something. I've also witnessed first hand some pretty freaky stuff in other locations too. If it's never happened to you yourself (yet), don't just dismiss it.