Keygrip, great post.
Personally, I'm amazed that people sell off their PPL books on eBay after they've got the license. Do these people think they're infallable and never forget anything, or that the stuff in there is no longer relevant to their flying now that they've got the ticket? I would only sell off my PPL books once I would replace them with something better (CPL/ATPL) or when I give up flying altogether.
We humans were not meant to fly. Any height above two meters is sufficient to kill you if you land with the wrong body part first. The stuff we do up there is dangerous, and there's two things that can help you when all goes pear shaped: experience and knowledge. PPRuNe gives me both the benefit of the experience of people on here that have way more experience than I have, and gives me the opportunity to acquire new knowledge (or refresh existing knowledge) as well - particularly if a question is posed of which I think "I should know that, but I don't". If an interesting question on here makes me grab my PPL books, or LASORS, or a POH, or something else to answer it - even better.