Why are contributions to the education of the broader public not valued much within academia? Scientists not only need to discover new knowledge but also have to share the knowledge to others. For the former, we have things like universities, collaborate groups and journals to take charge. For the latter, we have various forms from teaching, developing and maintaining softwares to writing or translating books, writing and editing in Wikipedia, answering (and asking) in SE, joining an academic club, working on a academic-related project, blogging, etc.

Besides the first two have significant weight in academia, the others seem to be light weight (some even say that they have zero weight) (example for Wikipedia, translating book). Although I understand the worry that I may spread myself too thin, I think the important thing is scheduling time wisely. I don't think they are deserved to be bad effective. In fact some scholarships (like this one) require me to describe "any examples of leadership and involvement in my university or home community". I have even seen some high rep users modestly proudly say that they are active users in SE in their websites. I see a conflict here. Can you explain why contribution to community is deprecated in academia?

A very interesting question from F'x: How can a researcher improve his contribution to society?
Scientists not only need to discover new knowledge but also have to share the knowledge to others. For the former, we have things like universities, collaborate groups and journals to take charge. For the latter, we have various forms from teaching, developing and maintaining softwares to writing or translating books, writing and editing in Wikipedia, answering (and asking) in SE, joining an academic club, working on a academic-related project, blogging, etc.


I think this is not correct. Discovering new knowledge is the actual research (valued on all levels), "sharing to others" is writing publications (valued so much that the common criticism is rather that publications count too much).

What you mean is a different type of knowledge dissemination, basically the education of the broader public. This is indeed currently not widely valued, but I am not convinced that this is a fault of the system. Essentially, when an university hires a researcher, they want a researcher. They are specifically looking for somebody that generates new knowledge, not somebody that is good at breaking down this new knowledge for the layman (this would be a science journalist, or somesuch), nor for somebody that mainly collects and summarizes the knowledge on Wikipedia or Stack Exchange. 

Hence, the answer to your question:


  When will contribution to community be valued?


If you understand this as "when will my contributions to community be comparatively valuable for applying to a research position as research results", then the answer will likely be "never".