From The London Evening Standard, Tuesday 18 July 1989, Alexander
Walker Column.

...I've had a little experience of the occult myself. Years ago, when
a sore on a finger looked as if it were settling down stubbornly to be
a wart for life, I went to my Wimpole Street physician.

He reached for his perscription pad and said facetiously: "If this
doesn't work, we'll try a witch."

"Oh, let's try a witch first," I said ("Never refuse an experience,"
said Oscar Wilde, who should have.) We did.

She charged me L3, cried the equivalent of "out, out damned spot", and
it vanished within the week. My doctor would have shamelessly charged
me 10 guineas.

There, I think, you have it: witchcraft is popular because it is a
service religion. It delivers.