Why do people make false accusations of Abuse or being Abused?

so many reasons why somebody may make things up, maybe too hurt somebody, maybe for attention, obviously they want something or want someone to feel something for them, example .. Janet was accusing Alfred of rape .. Janet was just upset with Alfred for cheating on him and wanted revenge you need to look at why the person is saying this, do they have a grudge against the person they are accusing, obviously there is some reason for it revenge tactic by women, a way to make someone feel sorry for somebody, if somebody just says it with no reason whatsoever then they need psychiatric help