Perhaps but then you get stuff like this https://bradfrost.com/blog/post/facebook-you-needy-sonofabit...

They need to play fair or GTFO

You get stuff like... obnoxious notifications?

Duolingo's notifications are borderline emotional blackmail ("don't make the owl sad!"), and Duolingo is a vastly profitable company that expressly targets school-aged children. But because it's not social media, it's... fine?

What does playing fair even mean in this context?