But like its usual in the case of Observable-based APIs, FRP techniques can help easily implement many use cases that would otherwise be rather hard to implement such as: pre-save the form in the background at each valid state, or even invalid (for example storing the invalid value in a cookie for later use) typical desktop features like undo/redo

This is why this is called template-driven forms, because both validation and binding are all setup in a declarative way at the level of the template.

You are probably wondering what we gained here. On the surface there is already a big gain: We can now unit test the form validation logic