I see your point, and I'd give you a piece of evidence to support your idea that mental illness diagnosis is an excuse. In the late 1800s, when department stores came into being, it was a huge change in how Americans purchased many items. Before these shopping emporiums, one would go to a general store, request an item that would be brought from the store room or order an item for later pick up. The opening of department stores was followed by a baffling phenomenon - massive shoplifting done by women and girls of middle and upper classes. The psychiatry industry came up with a diagnosis: kleptomania.

The characters Janice is discussing were twisted, unpleasant and malicious. Your observation that they made a good living out of performative misery is well said. It's also the key reason why we, as a society, must reverse the many-decades trend of replacing diagnosis with ethics.