More broadly, I think the mere availability of mindless entertainment reduces one's ability to do anything else. I observe this in myself and others. In order to willingly do useful things, I need to be bored. That's when I feel a need to do something, and if that "something" is not Instagram or YouTube, I go for the more salient things. So for me boredom is a very useful state to be in. If I can't get bored (if entertainment is immediately available) I will not do anything useful at all. I have to make a conscious decision to not access entertainment during the day in order to get anything done. Fortunately I can do that without much of a drain on my willpower reserves.

But my son (and his peers) grew up in a world where everyone has Internet at all times, and the problem is more severe there. I'm trying to convince him that the way he's doing things now (basically 8 hours of YouTube and games a day, and lots of missing homework) will cause much regret in the future and will lead to a much worse lifestyle. So far I have failed to convince him of that though.