A few things:

- Splitting your community is a concern. The classic example is multiplayer DLC: if not everyone can access it then it will risk low adoption.

- Presales and first week sales are hugely important to financing projects. Not many games achieve a long tail.

- Developers are expensive. Paying a team of artists and designers and programmers demands that they generate enough revenue to make it worthwhile.

AI opens this door because:

- Its capacity to be constrained fits neatly into mod frameworks.

- It's incredibly cheap to operate, compared to the human team.

- Users are comfortable with its SaaS model and so won't be deterred by a subscription model.