I agree. There is an implied assumption in the original post that people have the capacity to use that extra time for learning. If you are mentally drained from work and other personal problems, then the ability to learn during that time may not exist.
These activities are a form of comfort for some, a frustrating addiction for many. I think a lot of people would love to be free of these habits, but don't know where to direct that time or how else to recover energy.
They do this to precisely to try to ameliorate the hopelessness and exhaustion and to recover enough mental energy to face another day without going insane. Humans are not robots.