I sort of wonder whether they realized gamification works for certain kinds of tasks, but not for others, and then decided to design their language learning app

I sort of wonder whether they realized gamification works for certain kinds of tasks, but not for others, and then decided to design their language learning app for gamification, rather than designing a gamification system to support language learning. In other words, I don't think Duolingo's system can really make you fluent in a language, but what it seems to excel in is making you use Duolingo every day. In other other words, you always hear people talking about how long their streak is ("500 days!") rather than how well they speak the language.