(mild spoilers ahead)
Playing Her Story made me want to invent a term: "payoff purity". (I'm sure someone more academic than myself has already coined a similar term, but I haven't come across it yet.)
Payoff Purity: the degree at which your mechanical input and game's reward system sync with each other.
Example of poor payoff purity: Habitica, or any gamification thing where task / reward are unrelated or a one-way deal. Feels like working a job.
Example of high payoff purity: Journey, Her Story
Her Story's mechanic (search engine browsing) requires you to pay attention to the words in the videos, making this game more about watching stuff than anything else. And the reward for paying attention to Hannah/Eve's words, for knowing where to look next? More videos! The fact that the test/reward system loops isn't specifically the point, though it's common to pure payoff games. What I'm getting at is that your actions are rewarded in a very 1:1, organic, makes-sense kind of way, a way that doesn't feel like game mechanics at all, but rather the logical result of your efforts.
The payoff (more vids) mechanically benefits you by giving you a ton more videos to look at, which in turn gives you more keywords to search with, which lets you watch more videos. Nice!
Why it's worth caring about
When you can structure the payoff for doing something to be the main thing the player engages with, that's basically maximum intrinsic motivation, isn't it? You're keeping the player in the game and you're helping them enjoy where they are (the payoff from the last action) and simultaneously making them look forward to what's next.
I think most importantly, it makes the player engage with the game for its own sake instead of doing some task they don't love in order to get achievements or other unrelated rewards. These things are probably fine for some people, but you won't win any holistic design rewards.
Flash conclusion: "It's nice if rewards for your actions mechanically synergize with gameplay and lore."