Doing the steps and not going anywhere

If I made an actual step every time my teacher said "step" in two classes I observed today I could have had a nice walk.
I don't see them learning, I just see them stepping. Everything is done for them and when they make mistakes and do procedure incorrectly, she says "Oh, you just forgot to ______________". No, they didn't forget. In order to forget, you must have known it at some point.

It seems to be a common practice to have students work on their homework in class. This, I believe, is an American construct. I find it useless, but people feel attached to it (also, which part of the word homework says that the work is supposed to be done in class?). I saw a teacher give kids and upward of 20 minutes to do their homework. About 75% of the students, if they even bother to attempt the homework, are out of their seats and ready to head out the door within 5 minutes. Now, there is all this talk about not having enough time to go through the material that one is required to cover, but there seem to be so much wasted time. Am I observing an extreme case, or is this practice common? Here is a questions for all the teachers out there: How do you feel about homework time, how much do you give and is it really beneficial?