I have visited four of these Nadi experts.Following are my comments.
Your past is very accurate as the information is extracted telepathically from your own mind.The future is a guesswork and is sometimes true but most of the time false.The shock to the person trying to get his Jyotish is due to uncanny reading of your own mind due to which you become a believer.[All swamis and godmen use the same method.] I had taken one old Sanskrit and a clasical Tamil expert , they could not make head or tail of the script .The concerned people will always have not more than a few hundred strips with them.
The problem is with us who are stupid instead of fighting a problem try for a quick fix in a temple ,with a guru or swami, or we go to an astrologer. The entire society has this sickness of giving up when faced with a problem.
God will always listen to you ,you do not need a middleman.