Sometimes we find it distasteful to have things we're fully aware of explicitly spelled out. A trite quip here is "nobody wants to see how the sausage is made".

I would take it further and say that the more light we bring to this subject, the less it becomes the exclusive domain of snake oil salesmen and the "sales tips 101" type books, and the more inoculated the general public becomes to manipulation.

A self-help book that took off saying the quiet part out loud is How to Win Friends & Influence People. It predates the 'influencer'.