Gym memberships cost money and they don’t want you to come.
Free language learning apps (Duolingo) want your attention, but at what cost? Well to start, maybe the cost of delaying your progress.
If it’s too hard (spoiler alert, actually learning a language is hard) then users will go away. If users go away they they won’t be able to maximize their advertising revenue.
I remember that last time I used Duolingo. I chose an easy lesson simply to ensure that my streak was extended. Think about that, I was sacrificing an opportunity to learn, just so I could continue my streak. This is the downside of “gamification”.
Duolingo isn’t all bad however, they do make it easy to get started in your language of choice. If you’re thinking about starting to learn a language, Duolingo is a great place to start. Just be aware of the potential pitfalls and be ready to change things up once your progress slows, or you get bored (which will lead to slower progress).