Yes, lack of productive support for tooling, a language is much more than a grammar + semantics.

So imagine how you would design a language with dependent types that would match the productivity of Interface Builder when designer GUIs.

Or a being able to provide something like Unity.

Not only the whole interactive design process, but also the ability to ship UI components that can be integrated into the designer's toolbox.

How would a drag & drop action, or mouse click binding an event to a slot, reflect into the existing type definitions.