Those who can, do.
Those who can't, teach.
I think there is some truth in this, in that most creative writing programs turn out people who are qualified to teach creative writing, not necessarily people who are qualified to write.
Nevertheless, I also agree with those who say that the best teachers have a talent for teaching. It would be a pity if they didn't put it to use. But these are rare enough overall that the number of them teaching creative writing courses are going to be correspondingly few as well. What you normally get is someone who has little talent as a teacher or a writer. The ideal, of course, would be to find someone who is both.
I think if I was going to take a creative writing course, if I didn't know students who had taken the course before and could tell me whether the teacher was good or not, I would want to determine for myself that the teacher could at least do it him- or herself: write creatively, that is.
I am sure that at the very least there would be something in an academic literary magazine, and it would be an odd writer who didn't want to show their published work to someone who asked.