For the most part, people see a psychotherapist because they've got problems that they feel unable to fix on their own. Awareness of resistance to the psychotherapeutic process is almost as old as psychotherapy - it's a central concept in Freudian psychoanalysis.

"You have to be willing to help yourself" is perilously close to "psychotherapy only works on people who are capable of changing of their own volition", which calls into question the entire purpose of psychotherapy. If I could change my way of thinking through sheer force of will, why would I pay a professional $100 an hour to sit and listen while I do it? It evokes the classic defence of the quack - the spoon only bends if you truly believe in the power of the mind.

If that problem is framed as "some patients are too sick to treat", then at least it shifts the burden of responsibility onto the therapist; it's not the patient's fault that the psychotherapist lacks the neccesary tools to facilitate change. Blaming the patient for having a bad attitude just makes the profession of psychotherapy look ineffectual.