The point is: would you rather spend your time playing the game, or reading someone's stab in the dark on the mechanics of the game based on his/her personal experience and questionable expertise?
I can find out a lot of stuff on my own, but it never helps to read what someone else has figured out.
Analogy: I can figure out design patterns of programming on my own, but I can speed up the process if I read a book on it. Same with design patterns for happiness and success.
There are lots of things I consider possibilities now that were not even on my map before I read self-help books.
Personally, I agree (although I haven't actually read any books yet, but I'm interested). But I would much rather spend 100% of my time playing the game and 0% learning mechanics than I would spend 50% of my time playing and 50% learning mechanics. I imagine the anti-self-help attitude comes from looking at the 50/50 (or more extreme) people.
Isn't that what most people do, though? And most people are not living the optimal version of their lives, or anywhere close (optimal being defined as the life one wishes one had).
Before I started reading self-help materials, I was intellectually gifted but I was a mess in terms of communication with others, emotional stability, self-limiting beliefs, knowledge of possibilities in life, luminosity aka self-insight, strategicness aka getting shit done with a plan, etc.
Studying self-help materials for the past 5 years is the most important thing I've done in my life (a quite dramatic statement perhaps, but that's how it feels to me).
That's why I get a bit upset and argumentative when people slam self-help: it's a bit like saying I shouldn't have wasted my time reading all those things, and instead should have just plodded on in darkness.