Why are new encyclopedias being published when there is Wikipedia? Recently, I have noticed that I have been visiting Wikipedia more and more frequently for finding information on technical materials that I need for my work and research. Over time, I have noticed that many entries on Wikipedia are well-referenced and reliable and also, I have found it rather comprehensive, at least in my field of work and study. Consequently, I wonder if it is necessary to publish and/or purchase new technical encyclopedias? Is it merely because Wikipedia is not still very comprehensive or reliable that new encyclopedias are published or updated? If the answer is no, then what are the reasons that authors and publishers still invest on encyclopedias?
There are a number of specific policies and practices of Wikipedia that reflect judgment calls, and it's perfectly reasonable to treat them differently for different projects:


Above all, creators of another encyclopedia might want to exert editorial control over the product. The rest of this list expresses some of the specific ways they might do that.
Wikipedia explicitly aims to serve a general audience; another encyclopedia might be designed for an expert (or afficionado) audience in a certain field
Wikipedia contributors may be anonymous, and the majority are
Wikipedia maintains a strict egalitarian ideal, which makes it difficult for subject matter experts to exert special authority
Wikipedia's peer review mechanisms are very specific; publishers of another encyclopedia might design them differently
Wikipedia's standards for sourcing, and its threshold for inclusion, are very specific; publishers of another encyclopedia might design them differently
Wikipedia has very specific standards around copyright of text and media


On my connections to Wikipedia: I have been editing Wikipedia (almost exclusively the English language edition) as a volunteer since 2006. I designed the first formalized program to support university instructors assigning Wikipedia composition, on behalf of the Wikimedia Foundation, in 2010. I have run a Wikipedia training and consulting company, Wiki Strategies, since 2009. I have served as editor in chief of the Signpost, Wikipedia's volunteer-run newspaper, since August 2016.