"God is a Spirit," Jesus told the Samaritan woman at the well. That is something a lot of people have a problem with: spirits. Just because it isn't visible, it must be inferior (or scary). We only allow things we can see to impress us, even if they're totally unreal, like most of the special effects we see in the movies.
As long as it can be seen, it impresses us. Anything that's not seen, immediately receives the label "inferior," if not "irrelevant."
Perhaps if we exchange the word "spirit" for "supernatural," though, we might get a little bit more attention.
Pretty much everyone is somewhat interested in the supernatural, even if they have no interest whatsoever in spirits. Spirits are stuff for stories they used to scare kids with in the olden days. Supernatural is more like "now you're talking," because the stuff they watch on TV deals a lot with those things.
In reality, "spiritual" and "supernatural" is one and the same thing. Everything that cannot be explained in natural, physical terms stems from a realm that is beyond our natural realm we have thus far been able to observe, which is the spirit realm, and everything supernatural stems from the spirit world - of course, both sides.
It's just that by avoiding the term "spirits" we can avoid the biblical and conventional aspect of the supernatural.
Just as he did with sex, magic and a bunch of other things, the devil would like to claim the domain of the supernatural exclusively for himself, which he unfortunately manages to a large extent because of people's (and particularly Christians') fear of the supernatural.
C. S. Lewis wrote in his book “Miracles,” the following:
“Only Supernaturalists really see Nature. You must go a little away from her, and then turn round, and look back. Then at last the true landscape will become visible. You must have tasted, however briefly, the pure water from beyond the world before you can be distinctly conscious of the hot, salty tang of Nature’s current. To treat her as God, or as Everything, is to lose the whole pith and pleasure of her. Come out, look back, and then you will see…”
That’s in essence the point I’m trying to make with my ongoing eBook project “The Deeper Meaning of Everything:” that there is something more to see in nature than meets the eye, the handwriting and footprint of the supernatural, (that which we dare not call spiritual) … of God.