Why these four, and why nothing more
These calculate things that are true regardless of what you own — what a loan costs, what a withdrawal costs, which of two sets of terms is cheaper, how long money takes to double. Ordinary arithmetic, useful to anyone.
You will not find a life insurance needs calculator here, or a policy projection, or a retirement plan generator. Those tools assess a person and model a product, which is regulated activity and would require a licensed conversation about your actual circumstances — not a web page. A calculator that pretends otherwise is doing something it should not.
What these will do is make certain costs visible that are ordinarily invisible. That is the whole of the book’s argument, and you can test it here on your own numbers without buying anything or telling anyone who you are.