While I am both an amateur radio operator / license holder (VE3TIX), and a member of IEEE, I am not a professional engineer (P.Eng), or a educated / employed as an electrical / electronic engineer (EE). Let alone a RF engineer.
There are various reasons, like the amateur radio community is probably one hundredth of the size of the IT / programming community in any given country, there is simply a smaller pool of people to participate. Then there is the massive demographics difference of age. While amateur radio is still growing in popularity in USA and the rest of the world, the average age of hams are close to 60-65 years old, versus (early) 20s average for programming (my guess). Finally I have not seen a single person promote this forum to the numerous existing amateur radio forums and web sites: QSL.net, eHam.net, QRZ.com, AC6V, and the cornucopia of Yahoo and Google Groups. A lack of promotion means a lack of awareness.
Part of me finds it selfish to ask why isn't there more people willing to answer a particular question or class of questions. That seems like a failed approach to growth. A better question is how can the forum community foster better representation, relations, or build bridges to existing external communities. The first of which for me is that the community needs to be useful to the contributors, as well as the questioners. I see no advantage of me taking my own time to write up answers, draw schematic excerpts, and find online references I can link to if I am not confident that there is willingness of the group to do the same for me, when I have a question.
Secondary issues include that good questions and answers in electronics more often need visual representation (i.e. diagrams, typically schematics) and lack of online reference material suitable to linking to.
The lack, compared to the printed ("dead tree") library, of high quality legal and stable, freely available reference material to refer and link to compared to the massive amount of online material for StackOverflow available from university computer science programs. To take three examples, I don't know of anything available (legally) online that is anywhere near equivalent to Antennas by Krause (3rd edition is now out-of-print), Art of Electronics by Horowitz and Hill, and the ARRL Handbook by ARRL (2011 ed. link). To the best of my knowledge there is nothing comparable. Heck, there is isn't even enough available to be equivalent to the first 1-2 university-level electronics courses. Lessons in Electronic Circuits is perhaps the best, but it is unfinished, largely stalling since 2004.
Back to the Professional Engineer comments (@Brain Carlton), to the best of my imperfect knowledge professional engineers like lawyers, often avoid publicly giving even "unofficial" advice, in part due to professional liability concerns. I expect this extends to other working "engineers". So I expect there a historic cultural difference towards not sharing or helping of non-peers from within the electronic engineering community. Hams also have this cultural avoidance tendency to avoid giving RF advice to non-licensed amateurs, as these non-licensed usages have historically been dominated by illegal (Radiocommunication Regulations) activities such as unlicensed amplification of CB or Wi-Fi equipment, which when done incorrectly creates interference with other licensed radio operators (including the hams themselves).
Side note: In some countries the "engineer" job title is legally restricted to licensed professionals (Iron Ring), such as Canada, so I feel obliged to quote this title, in Canada they would tend to be electronic technicians, as I believe is the most common equivalent job title in Canada.