Many people ask why, since I am in fact a very experienced ghost hunter and spirit medium, I don't demonstrate actual spirit contact.
Simply put, the reward is small and the risk is great. Actually, people are in general more impressed and emotionally moved by the theatrical version than the real sťance, and I don't blame them.
Usually a genuine spirit contact takes time...something most people, especially Americans, aren't willing to spend waiting for results. Theatrical effects are instantaneous and controllable, which brings up another point.
Sometimes a real spirit contact, in spite of hours of preparation and at least an hour of convocation, just doesn't happen. That won't fly for public demonstrations.
...And speaking of publicness, as a spirit medium, you simply can't trust people to behave. Most will, but the exception can cost someone their life, sanity or well-being -- and in the end, most folks will assume it's all a trick anyway.
Ultimately, at the end of the day, for public demonsrations, I go to the theatrical event. Real seances with real ghosts in front of uninitiated, skeptical and fearful spectators who might panic and react badly? No, thanks...it just isn't worth it.