The article does address it:
The real question raised by McGuire's argument is whether we continue to value ebooks as books, or as webpages. Books are something we pay for. Webpages are things we read for free. Which model will win out?
Articles on web pages are paid for by advertising. Proposing using the same model for books that is used for articles is to propose that books be ad-supported.
The article is not about web accessibility for books.