[accessibility] What are good reasons for not releasing the source in 2019?

[easjolly at ix.netcom.com]

Ross Moore wrote: "Furthermore, it does not generalize to larger
publications like text-books, as authors and publishers can have very good
reasons for not wishing to release the source."

I don't understand why this is any longer the case.  Given the tools
available in today's digital environment, properly trained persons can
create an equivalent source from a print copy of a text-book.  In fact this
is essentially what many braille transcribers are forced to do.  This
situation currently leads to a considerable waste of resources in addition
to having a negative impact on students who can't get their text-books in a
timely manner. There must be a better way.

SusanJ