These can be valid within the context of the class, just as explaining grammar can be.
The operative word is "can."
Is this all there is? Grammar lecturers or clowns? Really?
That is mostly what I've come across- teachers who try to get by on just making friends with every student or those who basically just drill grammar or do questions in "the book." I'm not saying that's all there is, I'm saying that's mostly what I've seen.
I have always had this view of teaching here and even with the pressure to give all my time to one particular school this year, I have stood firm and said no.
That is the smart move.