Why are demons always invisible?

Certain parapsychologists who investigate demonic activity - and no, I'm NOT referring to the ridiculous "The Demon Files" where an ex-police officer goes in and starts yelling at demons as if they're human men who bash women up who can be expelled with exclusively Catholic rites - and some intuitives (many detest the term "Psychic" because so many fakes use that label and get away with it) as well as demonologists who are clairsentient/sensitives/intuitives would answer this question by replying that demons and other entities inhabit a level of existence which is normally beyond the 5 physical senses of humans.

Nevertheless, when a demonic entity is present, almost any individual will sense something is wrong and want to move away from the area or, in cases of obsession, oppression and possession (as examples of how demonic forces negatively influence people), from the individual/s concerned.

Spirit entities inhabit a realm which overlaps ours but which involves EMF energy and it is this that genuine parapsychologists, intuitives etc. are looking for and genuine intuitives are extremely sensitive to. There are very few psychics or intuitives who will physically see an entity just as they would see a normal, living breathing person because, in most cases, an intuitive senses entities and some do so very much in their 'mind's eye' (a little bit like one's imagination but visualising the entity without imagination being involved) i.e. clairvoyance (literally "clear seeing" in French).

There are indeed some videos of what appear to be demonic entities but none have been scientifically evaluated to determine their validity. One is available via YouTube which purports to show a demon standing over the physical body of a dying patient (in a Hospital). Whether that is genuine remains to be seen. Personally, I believe that such entities have the ability to determine whether they wish to be seen or not but that they are not able to hide their malevolent presence from genuine psychics and nor from genuine exorcists.