The main reason is pretty obviously that the core of their games stays mostly the same, rehashed over and over. Souls games are very minimalistic in their production values. What other AAA these days could accept NPCs as just static vendors with a couple lines for their entire storyline, no animations, no lip movement, nothing but a generic NPC template with an outfit to set them apart? Only Nintendo comes to mind. This is incredibily simplistic, cheap and fast to make, and their success hinges on their competent direction. From games are super simplistic in many aspects that western AAA's spend vast amounts of time and effort into. And that's perfectly ok. You concentrate on what you are good at, and From does a lot of great things that aren't expensive time consuming high production value things. Great combat system, great art design, world building, level design. The core gameplay loop is fantastic. Having a very experienced crew making similar games year after year is a massive advantage in efficiency compared to disparate team trying to cobble together a massively overbloated design over a number of years, even when helmed by very experienced leads.
People have been happy with this so far, but I don't think they should just rest on their laurels. There will come a point where the core of these Soulsborne games is so overdone the average gamer will lose interest, that is if they don't evolve it in a more radical way. To me it's surprising they've kept their engine for this long, but I wouldn't be surprised if they moved to UE5 eventually like most other teams. That alone would probably shift things considerably, and also require a lot of retraining for a team that's cobbled up similar games using the same old tools over and over. With more detail comes more expectations of production value for things like NPCs From has kept minimalist so far. All these things threaten to increase the length of their development cycles in the future.
Of course From probably does adhere to some problematic aspects of Japanese working culture too, that does come at the expense of the workers there compared to some western studios, but it heavily depends on the studio. On the other hand some western studios might have really toxic cultures inside them, despite having pretentions about catering more to the employees. In Japan the work culture's more put up and shut up, which has its upsides and downsides. Less drama, but the nail that sticks out gets hammered down.
