Self-help books from different authors on unrelated subjects tend to share a structure so closely that readers can predict what each chapter will do. The convergence is functional rather than lazy.
The book has to change behaviour, not just inform
A reader who finishes a self-help book and does nothing differently has not received what they paid for, so the writing is organised around application rather than around exposition.
That means the argument must be simple enough to be remembered at the moment it is needed, which is usually days later and in an unrelated setting.
Structures that support recall win out, and structures that reflect the genuine complexity of the subject are edited away.
Naming the problem comes first for a reason
The opening section describes a difficulty the reader recognises and gives it a name, which is the point at which the reader decides the book is about them.
Naming also does persuasive work, because a problem with a label feels tractable in a way that a vague dissatisfaction does not.
Once the reader accepts the diagnosis, they have implicitly accepted the framework that follows from it, and the rest of the book is comparatively easy to deliver.
The framework is the product
A named sequence of steps, stages or categories gives the reader something portable to carry away, and it is what gets repeated when they describe the book to somebody else.
Frameworks also make books teachable, which matters because a large part of the category's revenue comes from courses, talks and workshops built on the same material.
An argument that resists being drawn on a whiteboard is worth less commercially than one that can be, regardless of which is more accurate.
Stories carry the framework between chapters
Each stage is illustrated with a case, usually of somebody who applied it successfully, and the case is what the reader will actually remember.
Repetition across chapters is deliberate, since the reader is being trained in a pattern rather than led through an argument that develops.
What the structure suppresses
Uncertainty, conditions and cases where the advice does not apply all interrupt the pattern, so they are compressed into a late chapter or dropped.
The result is a category that reads with unusual confidence, and that confidence is a property of the structure the books are written in rather than of the evidence behind them.