English Education folks will be teaching writing, so they'd better know their craft.
They will be communicating with parents, colleagues, the community, administrators, and students in writing. Not writing well will lessen their credibility.
It's a very tough challenge for teachers to assign and assess writing in a wide variety of genre if they have not had writing experience in those genre themselves. Teaching language arts effectively can never be a "do as I say, not as I do" practice.