Many teachers/professors I had in my youth asked the class to read the material before lecture so the lecture could be a summary and then most of the time spent asking questions/discussing the topic. Few students actually did so.
Just give them a weekly quiz based on the content and grade that.
My math teacher in high school gave us a 15 minute test every week and would just randomly pick 4 students who must hand it in of which one presents their solution giving the teacher time to grade the tests. Doing something every week makes it less stressful.
It's not a matter of asking, it's mandatory. Reading is your homework, and if you don't read the night before you won't be able to do your problems and get help of you need it the day of.
I suppose it's a question of pedagogy to determine how (and how much) teachers should encourage students to present behaviors that make them more likely to learn. My experience (and many others) is that inverting the classroom ends up with the majority of the students not doing the assigned reading/listening/watching.
Most students do their math homework begrudgingly because they get in trouble otherwise; this does not mean that doing the assigned problems does not help them learn...
