First, this is very insightful--I think most people should go through this exact analysis before architecting a system.
As others have said, the use is multiplayer, and that's because you need everyone to see your changes ASAP for the app to feel good. But more broadly, the storage industry has been trying to build something that's consistent, low latency, and multiuser for a long time. That's super hard, just from a physics point of view there's generally a tradeoff between consistency and latency. So I think people are trying different models to get there, and a lot of that experimentation (not all, cf Yugabyte or Cockroach) is happening with SQLite.
As others have said, the use is multiplayer, and that's because you need everyone to see your changes ASAP for the app to feel good. But more broadly, the storage industry has been trying to build something that's consistent, low latency, and multiuser for a long time. That's super hard, just from a physics point of view there's generally a tradeoff between consistency and latency. So I think people are trying different models to get there, and a lot of that experimentation (not all, cf Yugabyte or Cockroach) is happening with SQLite.