I mean obliged in the sense that it's just good design.
If I'm a dev, and I make a game that's impossible even on easy, nobody's going to play that shit except streamers because it won't be any fun without someone to commiserate on how awful it is to play my game. Indeed the whole point of picking difficulty is itself a way for the player to self-modulate the experience, which is why streamerbait games don't usually have one; the whole point is that they're awful to play and the streamer gets to scream and cry.
Whether the player payed money for it or not has nothing to do with it being a good game or not, the rules are the same either way. And that's what's obliging them, the desire for the game to be good. A porn game with 2 H-scenes and 14 hours of exposition is not a good porn game, pirated or otherwise.
They're obliged to not make the point of the game worthless in the same way that a developer is obliged to not set the volume defaults to Earrape and make the main menu music a deepfried Soviet Anthem.