I know of several professional writers who continue to use whatever obsolete word processor they first learned to use way back when (Wordstar, Macwrite, Protext, etc). However, they also have a system for getting the text into something standard-ish (plain text, rtf, whatever) so they can send their stuff to an editor once it’s written.
What I was thinking of was people like those writers. I agree that it’s really incredibly stupid and inconsiderate to try to send someone else a thing in a format that nothing made in this century knows how to open.