it's actually because layout-via-code for arbitrary documents is a humblingly complex problem, so leveraging existing layout engines is preferred.
This impressive effort looks far better than what I'd achieve, but when this approach has been tried before, it is eventually discovered that few organizations have the resources to maintain a rendering engine long-term.
This impressive effort looks far better than what I'd achieve, but when this approach has been tried before, it is eventually discovered that few organizations have the resources to maintain a rendering engine long-term.