The necessity of sex scenes in American Horror Story for storytelling is debatable. On one hand, they can provide a deeper understanding of the characters' flaws and desires. By showing their sexual encounters, we can see how their primal instincts interact with the horror elements around them. This can lead to interesting character development. For example, a character's sexual indiscretion might open the door to a supernatural curse. On the other hand, the show could rely more on psychological horror, spooky settings, and plot twists without the use of sex scenes. It really depends on the creative vision of the showrunners and what they want to convey about the nature of horror and human nature.
Well, in a way, they can be. They help to show the complex nature of the characters. For example, if a character is driven by lust and this leads to their downfall, the sex scene is a part of that story arc. But on the other hand, the show could still tell its horror stories without them, just maybe not with the same level of shock value.
I don't think they are entirely necessary. The horror can be achieved through other means like suspense, mystery, and grotesque imagery. However, they do add a certain edginess and can sometimes be used to explore the darker aspects of human relationships within the horror context.