Though to be fair, sometimes those anecdotes are useful. I like examples, especially ones where an idea is applied to a situation that resembles my own. Also repetition is helpful to actually have a concept sink in.
Also, what's filler for you may be the most relevant section for someone else (e.g. an anecdote that matches their situation but not yours, or necessary repetition).
Also, I think software engineers, at least, have a bias to optimize for concision that can sometimes be counterproductive. For instance, I doubt a moderately long article that fully explains the core concept of cognitive behavior therapy would be as successful at actually changing the behavior of a depressed person than a more "redundant" book-length version. Maybe the short version would still work for some people, but that doesn't mean that's the best version for the majority of people.
If it takes repetition or length to do it, so be it.
Some books even recommend you read them a second time for that purpose, like Getting Things Done and How To Win Friends and Influence People.
I actually think this book is one of the rarer examples where the various stories and anecdotes that are sometimes seen (rightly) as “padding”, are actually in this case quite effective at getting the message across in quite a memorable way.
It’s been a while since I read it but I seem to recall a lot of similarly effective stories about airline pilots too.
On regular days with regular mood, I say it's just easy way of milking people, and that self-help genre died soon after being born, i.e. back in the days of Dale Carnegie.
Happened with all the self-help or self-improvement books I've touched.
The most excessive example of this being "getting things done" which was very trendy about ten years ago: the first third of the book were literally about the author bragging about results (but without any way to fact-check).