 How could selling their work actually harm some authors' interests?
Authors who share their works in this way aren’t selling them, and even authors with purposes higher than money depend on sales to make a living. Suppose that selling their work would actually harm their interests by shrinking their audience, reducing their impact, and distorting their professional goals by steering them toward popular topics and away from the specialized questions on which they are experts. Creative people who live by royalties, such as novelists, musicians, and moviemakers, may consider this scholarly tradition a burden and sacrifice for scholars. Scholars can afford to ignore sales because they have salaries and research grants to take the place of royalties. Authors who work for royalties have reason to compromise and settle for the smaller audience of paying customers.
 The cost to read the work could result in a smaller audience.
 It could steer them toward writing about popular topics rather than writing about their expertise.  Libraries may decide not to purchase the work because of the cost involved for multiple copies.  They may never reach a global audience.  The cost to read the work could result in a smaller audience.