I don't know why, either, but it kind of turns me on as well. It doesn't even have to be an incest story, really. Any kind of mind control (as in hypnosis instead of BDSM) is a turn on for me.
There are many ways this could go...
A woman could go to a hypnotist to work on losing weight or to quit smoking, and while she is under he could implant an idea into her mind... She would let her inhibitions go while under hypnosis (since that's what it does...it doesn't "force" anyone to do something they never would). She could become a "sex slave" to her hubby... Or she could let her inner slut out and go "have fun"...
A couple (or group of friends on a "double (etc) date") could go to a comedy club to watch a comedic hypnotist and the woman (or maybe each woman from the group of friends) could be one of the volunteers who gets up on stage. The show goes on and funny things happen...but maybe the hypnotist implants an idea into the woman(women)'s mind that lets her(their) inhibitions go!
Or, it could go the incest route... And the father (or any "respect adult in the family") could gain control of the daughter's mind, etc.
