What is radical, new, or innovative in D. F. McKenzie’s description of bibliography as "a sociology of texts"?

McKenzie opened up bibliography as a field by incorporating what he called the "social processes" of how texts are produced and disseminated. He argued that the way texts are produced and distributed—and which texts are printed and reprinted—documents larger changes in a society and that these texts, in turn, influence social change. He allowed the field of bibliography to open in new ways to encompass how economic, social, and political factors impact publishing and how publishing exerts an influence over them. 
McKenzie looked at how various social forces determined what format a book or text appeared in and how it was distributed through a culture. He studied why certain texts were written or produced, why they were rewritten and reproduced in particular ways, and why some books were allowed to quietly fade into obscurity. He was innovative in asserting that book publishing—and republishing—does not occur in a vacuum divorced from other cultural influences. It is not simply the "best" or the most marketable books that get printed or reprinted, but the books that reflect, reproduce, and reinforce certain perceived social needs. As a case in point, McKenzie examined how the production of two texts in New Zealand, the 1835 Declaration of Independence and 1840 Treaty of Waitangi, helped authorize the transfer of sovereign power from the Maori to the British. 
McKenzie was also an innovator in other forms of media; he integrated film, music, and video into the the field of bibliography.