I am yet to find many students who use their free time in productive things. Can you tell me what productive things the students do?
Anyway, assignments are to help the students apply what they learn in class. If you think they are useless please explain to your teacher why they should be abolished. If you do your assignments seriously you will learn a lot. But, most students copy from others so they find the assignments useless. If you are copying, you are making the assignment useless. Don't blame the teacher for it.
Most of the IIT students spend their free time on the internet. Are you serious that they are doing something productive? I would love to meet these productive bunch of students. Please divert them to IIT Roorkee.