I don't think many lives are changed by self-help books. People who are actively trying to change their lives often read self-help books, and then misattribute any positive result to the book. Then they recommend the book to others, and it's either mindless blather, or common-sense tropes wrapped in a bow, or something that reinforces a decision they've already made. Someone decides they need to focus on something, and then reads a book about it while they're focused on it. They already changed their life before they read the book, by making the decision to change.
No one is changed by a religious text if they are already a religious person who largely agrees with the philosophy. No one changes their diet if they haven't already made a decision to eat healthier. No one GETS.RICH.QUICK if they weren't already entrepreneurial.
Yeah, maybe these books impacted people in some way. But they were already 99% of the way there. Recommending them to someone who isn't also 99% of the way there isn't going to change a thing.
The older I get the more obvious it is that there are no new ideas, there's just new branding.