It could probably but I believe maintaining these two would probably be more work than accepting the drawbacks. Another advantage of supporting full-fledged React is that (in the near future) we can allow Javascript in the rendering engine, meaning that components can recompute themselves and pull their own data in. We will see where that goes!

Yes, that sounds interesting, and I sincerely hope that a future release of React manages to simplify use cases such as SSG with build-time JS.