In general, activity and “retention” - “sticky” players who keep playing - are valuable, because loyal customers are likely to keep buying your new products, as long as the products can satisfy their needs.
While there are nuances to it (notably, the challenge of delivering products that satisfy users), this is such obvious truism that I don’t think you’d object to it. In fact, I can see you saying the same thing in a different circumstance, when it’s your turn to stress the importance of user loyalty.
Now in particular:
WE is a MS subsidiary, meaning the money they make isn’t their own. Their funding is not drawn from their own profit, but allocated by their boss depending on company strategy and their performance. And corporate Key Performance Indicators account for factors other than direct profit.
We don’t know how exactly Microsoft measures World’s Edge’s (or any of its subsidiaries’) success, but we do have a clue.
In the Bloomberg report revealing that MS has been demanding an extreme 30% profit margin (seldom achievable in the industry) from its game departments since “fall 2023”, there’s this part:
Xbox offers its developers a credit, which it calls “member-weighted value” and is calculated based on several factors, such as the number of hours that Game Pass players collectively spend on a particular title. The opaque formula seems to favor games in which players can spend the most amount of hours, such as online multiplayer titles, according to people familiar with the calculations.
In other words, total hours played by users is a metric that MS tracks and values highly.
People keep playing the game matters to WE, that’s why they have been developing all these different replayable roguelite modes - to harvest longer gameplay hours from casual users who don’t play competitive multiplayer.