a. Those who made heavy use of e-mail, and where "adapted" to the user interface.
b. Those who had problems with the UI(replying to all their emails, etc...)
Of those two camps: those in camp `a` where unlikely to switch. That would have interfered with their workflow.
The publishers seem too attached to their licensing schemes. Speech-to-text and text-to-speech are here to stay and this is not a surprise for anyone. Publishers should catch up.