I think it's a good use of time, especially in an English class, because the beauty of Shakespeare never really came out for me until I read it word by word and knew enough to perform a bit of it. It wasn't created to be read, it was created to be performed, and I didn't pick up on all the nuances, humor, and craft that make it really good until I freed myself from reading it from paper. I'm likely a better writer because I've been forced to read poetry and plays in that way.

I expect that he didn't substantiate his claim for the same reason the original poster didn't substantiate his claim that learning C is a good use of time - people around here who have done both likely appreciate the value of the task.

Meta-point: I think a lot of people around here who argue "school is worthless, why am I doing this useless task" will point to this sort of exercise without asking or understanding why it's done. I certainly felt the same way when I was memorizing Shakespeare. While it's important to think for yourself, it's also important to take the advice of those who have more experience than you do, and when I see these threads I think many of the commentators haven't learned both lessons.