I'm a high school math teacher, and I absolutely agree with the OP.
My classes have what we lovingly call the "20 minute rule."
You need to spend 20 minutes per night doing your math homework. No texting, no snacking, no Facebook, no phone... 20 minutes of quality time with a pencil (or pen) and your math textbook.
At the end of those 20 minutes, finished or not, you can close the book.
If you're the only one who struggled, I'll expect to see you in extra help. If everyone struggled, then I messed up-- either my explanation wasn't clear or I underestimated the difficulty or length of the assignment.
You're also allowed to miss, then make up for full credit, up to 3 assignments per marking periods. Hey, sometimes life gets in the way of homework. Either you come home sick, or it's Grandma's birthday, or the appointment at the orthodontist's runs long.
There are no "math emergencies" that should require any kid to spend hours on my math homework.
I wish more teachers, at the end of a long day, had to spend a few hours helping their young kids with homework. I think they would see the frustration of a kid who KNOWS he's doing busy work, and the fear in the eyes of a conscientious kid who simply doesn't get the material but needs to finish it.
I have 180 days in which to cover the syllabus. It's my job to ensure that it's done well and that I've utilized my time well. I work from bell to bell, we don't play games or have days when we ease up. If you miss a day of my class, you've missed a lot. Miss a week, and you're in a pretty deep hole. But 180 days of one 38 minute class, plus 20 minutes of homework per day, is all I need.