What I'm seeing for me (and it's incomplete, it might be a fiasco in a year) is that it keeps me doing at least some daily roadwork. Once you get to reading news/magazines/whatever (that's how my father expanded his ESL vocabulary) or childrens books, you can start to work beyond. The real hazard is that once you break the chain, the incentive to do something (even when you are tired) is gone, then you probably drop it altogether. So I see the gamification of 'keep the streak' as helpful.