Academics can contribute plenty of general subject knowledge that isn't original research. And they're unlikely to want to contribute original research, because they'd rather get it published in a journal, where it counts for boosting their career. Once it's published there, it can be cited, so it's fair game for Wikipedia.
I think this is absolutely the case. All this discussion about publish-or-perish or rewards is completely disngenuous. Sure, academics want their own work published, and they couldn't get past Wikipedia's original work prohibition, but academics want correct information out there just as much as anybody and hate seeing stubs or bad info and would happily contribute.
A much more plausible explanation is simply that academia moves slowly and ponderously, and won't really change to accommodate anything new until long after it's established in society at large. The generation that has grown up with the internet are still mostly undergrads and PhD students (like me). Come back in a decade or two, and I think there'll be a lot more experts contributing to Wikipedia.
I think just about all these people have retired.
No the real problem with wikipedia is that they have ALWAYS been hostile to contributions by experts, like Fox News repelling climatogists. TFA mentions Citizenpedia, remember Wikipedia had TWO founders, one of whom got so disgusted with the anti-expert atmosphere he forked the project. His project didn't become popular, probably because 1) Wikipedia is always at the top of Google's searches, 2) Wikipedia is full of the cruft the public demands, like Anime, American Idol, and the aforementioned professional wrestlers which even the editors want to get rid of but can't keep up, and 3) because of 2), see 1) again.
Citizenpedia failed, but Wikipedia's still broken. So we get Scholarpedia. And then it's still broken. So we get Knol. And Wikipedia is still broken, people know it's broken, but it's at the top of the searches. The only reliable way to get an expert to contribute to an article and have it not get reverted is for an editor to plaster a "This topic needs attention from an expert" which doesn't happen that often. And even then, the expert's contribution will be "fixed" and "improved" until it's as factually accurate as your typical newspaper's sci/med reporting i.e. wrong (see any reporting in the last month about radiation).
Wikipedia will never improve it's reliability until Jimmy Wales and his cabal of editors who treat it as their own personal sandbox are given the heave-ho. Which isn't going to happen, because it IS their own personal sandbox.
What, citation needed? Anything from Sanger will do. Here's one from the relevant era: http://www.kuro5hin.org/story/2004/12/30/142458/25