I believe some people believe they are actually have the gift.
I used to go to the spiritualist church and see mediums every week. They didn't get paid a single penny so there was no money in it for them.
I don't believe they were charlatans, I believe they believed they had the gift.
I had many messages from mediums that were great, but nothing so mind blowing it could make me believe 100%. I was told a lot of things that were true; things that no one else could have known had happened unless they lived in my house with me. I have seen some good mediums who have got some stuff spot on, but nothing that gave me no choice but to believe, if that makes sense.
I am an atheist now and left spiritualism years ago when I grew up and questioned it.
I am not sure how these mediums did manage to get things right, especially as all I ever did was say yes or no and never handed them the answers like so many people do. Some messages were great, some were just so crap it was laughable. I had messages saying things about my granddad, how my room was decorated, the date my mum's first boyfriend died (my mum was with me) something about my son and various other things, and these were not things we hand fed them. I refused to say anything but yes or no.
I don't know how they do it. I think there is something more than just reading body language because my mums body language couldn't have given out the date of her boyfriend's death, but I don't believe they are actually communicating with spirits.