My boss stopped learning Spanish on Duolingo when he lost his streak. It's a powerful motivator even if it's not a "true streak" due to streak freezes and such. My streak is at 1436 and if I lost it, I wouldn't stop Duolingo because I actually like it to learn, but the streak does make me happier, haha. I think I've had 2 days in the last few years of streak freezes due to 1 day forgetting and 1 day the site not savi…
In the context you mentioned it, the streak sounds like a powerful demotivator. This is a more general problem with gamification and external rewards: they are just as good demotivators as they are motivators, if not more so. This is why I wanted to turn off streaks when I was using Duolingo. I knew it was just a matter of time before I had my streak broken, and I was very concerned about what would happen then.
The gamification requires two coordinating motivations— secondarily the game mechanics, and primarily learning a language. Duolingo won't replace candy crush for non-language-learners. I imagine folks significantly discouraged by poor game performance without doing some serious learning first just aren’t motivated enough to practice their language skills in an app.
Personally, I’m not motivated by gamification at all and am content to ignore it. It is noisy, however, and I also wouldn’t mind the ability to shut it off.