I think hypnosis is no longer prevalent in movies because we now know it can't actually do anything magical. It can't make you do stuff that you are strongly opposed to, and it can't make you remember things from past lives. It can, however, make you remember things that never really happened to you, which is something scary in itself. But back then people were actually afraid that you could be hypnotized and turned into a werewolf or forced to kill people. Ok, so no one thought they were going to turn into a werewolf, but the killing people was a concern for some.
The last movie I saw that had hypnosis in it was The Curse of the Jade Scorpion. What a horrible movie. Maybe that's why movies no longer feature hypnosis, cause Woody Allen killed it for the rest of us.