Like sex feels good, so does sin and people are weak for the pleasures of the flesh.
Not necessarily meaning the actual flesh, but also the pleasures of this world.
I battle with my appreciation for my mind ... I REALLY think I have my ducks in a row and I write as if I DO (tag line) and to me, that is sin if I dwell on it.
I don't need an exorcist, but I can imagine others getting wrapped up in various elements of themSELVES that they think they are possessed.
The born again Christian can come boldly to the throne of Grace and find mercy in a time of need and THAT is a cleansing experience every Christian is familiar with.
However, in some (comparatively rare) cases demonic possession is exactly what is going on. Keep in mind that in Jesus' public earthly ministry, He was quite often called on to exercise His power as an exorcist.