In the past two decades, work has emerged on how unknowns are socially constructed and why. Many of the explanations for the construction of unknowns are, for all practical purposes, functionalist explanations.  The crudest version of a functionalist explanation presumes that constructing unknowns benefits the agents doing the constructing.  Lies and secrecy fit this description, but so does the craft of manufacturing doubt notoriously honed by the tobacco industry and more recently by other interests. Sometimes these functions can inhere in some unlikely places. For instance, check out my response to a colleague who asked me about the functions of innumeracy.  

However, back in the 1930's the sociologist Robert K. Merton argued that there can be unintended functions (which he called "latent"), and this insight also has been mined by social scientists and psychologists who claim that our most ingrained cognitive and social habits have evolved to be well-adapted to our environment, without individual intent or group conspiracy.  Merton, by the way, also had a few things to say about ignorance.

There is a growing literature on the general topic of "agnotology", how unknowns are constructed socially and culturally. The edited book with the title "Agnotology" (Proctor and Schiebinger, 2008) is an excellent example.  My chapter in their book presents a perspective on "social" theories about how ignorance gets constructed. Many of the other chapters in this book reward the reader; see the TOC to whet your appetite. The Routledge International Handbook of Ignorance Studies, edited by Matthias Gross and Linsey McGoey, is now in its second edition and it ranges across several disciplines and philosophical perspectives.  You can get an idea of how much work has been going on in this area since the first edition in 2015 by perusing my Afterword chapter at the end of the Handbook.