They may not drive the traffic of Stackoverflow, but from what I've seen most of them are great sources of information for their particular topics. There are several other Stackexchanges I personally have found quite useful (ubuntu, tex, cooking, gaming, and homebrew mainly). I also enjoy just reading popular questions and answers from various sites as they can be quite interesting. Some examples:
I think programmers are always very trendy concerning new services. Think about how reddit was mostly programmers/startups at first or how facebook evolved from being a very specific audience. It'll take some time but in a few years everyone will be as quick as programmers to "google it". And when that happens, the other stackoverflow will certainly get a big bump.
Also, I think for some stackoverflow, it's not enough to tweak the colors.. Some of them might need a real disruptive tool to make it happen. For instance, the cooking one could have a hardware adapters to be used in the kitchen. Ok, that was a silly example, but I hope you get the idea.
It's not likely to ever produce another massive category product hit like Stackoverflow. Such success requires very high levels of specialization and dedication (not to mention a category big enough to begin with; all of which are already dominated by very large competitors, eg cooking / recipes).
Why would cooking experts or financial pros be drawn to Stack Exchange? They won't be. They'll stick to sites dedicated to those things that possess a very narrow focus, where the quality of content is likely to be higher.
It was an interesting attempt on Stack's part to spread out, but who really thought the end result would be them taking over every category?
Just take a look at Personal Finance / Money. That's a huge category that is very lucrative. Yet they're getting a whopping 5 questions per day for a three year old site, and a mere 7,200 visits per day. Why? Because "money.stackexchange.com" can never be promoted properly as a brand, it can never carry any kind of reputation as a separate product. An average person isn't going to buy into the notion that that site possesses authority on personal financial matters.
Guess it's a different viewpoint. Does everything need to dominate other areas? Why not focus on one thing (in this case question-answer) and simple become the best in that area?
I prefer if companies and sites focus on becoming the best in their area rather than continually pivoting to seek more eyeballs/profit.
The problem stackexchange faces now isn't failure, failure is easy to spot and often straightforward to fix. Instead they risk not living up to their potential, and not by a small amount but by orders of magnitude. With enough effort they could be the new backbone of q&a and forums on the entire web, but they've instead settled into a much smaller niche where they feel more comfortable.
The niche sites are comparatively tiny, but they are useful - I've found answers I needed, and if they weren't there (since the post count is low, as you say), I got great, rapid answers when I asked them.
http://travel.stackexchange.com/questions/19941/one-foot-in-...
http://english.stackexchange.com/questions/1216/what-is-the-...
http://physics.stackexchange.com/questions/75459/why-do-chim...
http://skeptics.stackexchange.com/questions/17578/did-9-11-l...