I did a bit of reading on that awhile back.
Actually there was supposed to be more "success" with transcutanial electrical- basically skin electrodes placed behind the ears, where the conductivity to the brain was the best. Only low voltages are used, obviously.
IIRC, there was a lot of dispute over whether this effect was truly "verified" at all or simply uncontrolled pseudoscience. If it doesn't work on skeptics, that would be a problem. There's also a false double blind effect- say you sometimes energize it and sometimes you don't, but the magnetic field is mildly detectable anyways. If nothing else, there's probably a vibration in the coil. Or maybe it has some trivial twitch-inducing effect you might notice.
But let's say it doesn't have any actual effect on the brain- yet if you TELL people it's supposed to give a near-death quasi-religious experience, and they feel anything from the magnetic field, the double-blind procedure is now invalid and the placebo effect is free to take them anywhere.