> your perfect design down to the pixel
> Surely it is an obvious next step to offer export to e.g. React, React Native, SwiftUI…?
These UI frameworks do not really operate in a "down to the pixel" way and so getting correspondance between a bitmap design and a representation in the UI framework is far from an "obvious next step" (if it were trivial to add such a feature, then of course the developers of these tools would add it).
Various concerns that aren't captured in the bitmap design - like how your screens transition from one to another, etc - can dramatically affect how the UI is implemented in a target framework. This is the job of UI engineers.
Well, used to be. Now it's vibe code all the way down.