In an ideal universe, trained educators and/or leading experts in their field would exclusively write self-help books. We do not live in an ideal universe.
Some of the stories behind these non-adaptations would make pretty good movies of their own (mostly comedies, with some hints of psychological horror).
We go to geniuses for hot takes on everything, regardless of whether the subject is in the 'expert's' wheelhouse or their opinion on it belongs closer to the outhouse.