Keeping the game a purposefully obtuse niche thing might make sense, depending on the values of the developer. It's possible to not be interested growing the dev team creatively, like most novelists are perfectly happy just writing by themselves. Solo gamedev is cheap, you basically just need to feed yourself and be able to run a computer, so in case you just want to work on the game all day, a very modest wage has you covered there.
Extra money never hurts though, so why not try to grow as much as you can? Well, there's the thing of interacting with your player base, which might be the most interesting social interaction you get if you live and breathe the game. The more successful you grow, the bigger the player base grows and the bigger the status difference between you and a random player becomes.
If it's just you and a few dozen players, it's basically just a social hangout with you providing some interesting entertainment. If it's a few hundred players, it's no longer quite that, but it's still a manageable community where you can have discussions with people. Once things go big enough, the emergent community stuff isn't going to work anymore, and you might be too big of a deal yourself to be able to do random chat and not have things go weird. You might end up having to either get some people as community moderators (you wanted to develop a game full-time, not work as a manager, remember), or just go into radio silence and lose the social venue. And now working on the game is crappier than it used to be, like providing entertainment for a social hangout, but now you need an opaque wall between you and the other people who keep throwing beer bottles at you and each other, dismantling the furniture and lighting fires. So why were you doing this again?