It is an extra step and time consuming to have to continually click the "annotate" button when our teachers don't actually want to annotate anything. If the student submits a photo as their assignment, the teacher must click the "annotate" button in order to even zoom in or out of the photo, so they can see the whole image.
Since the photo appears in a small sized box, and the submitted photo is not resized to fit in said box, just about any photo submitted by a student will need to be zoomed in or out to see properly.
I have attached a photo example of what it looks like from the teacher's perspective when a student submits a photo for their assignment.