In addition to what's already said by other posters, I also think that because these ghouls are so rich and already have everything they could have in life, they end up looking for what's left to own and exploit.

Things like drug fueled mansion parties with lots of women to take advantage of, stops being enough. When there's nothing else left to own, and all other types of exploitation have been pushed to their maximum, they have to seek out something more extreme to scratch that itch, like a porn addict who becomes desensitized and has to seek out more extreme material.

Eventually what's left are the types of exploitation that are considered the most taboo in society.