It is always the case. Even if you model app state in a functional way, the state is still somewhere, for example a haskell program may be pure but only because

It is always the case. Even if you model app state in a functional way, the state is still somewhere, for example a haskell program may be pure but only because it pushed the unsafePerformIO call into the runtime. UIs always have additonal state that is not modeled in the backend, we can only reduce the surface area of code that is stateful, but we can't outright remove it, it is essential complexity in all UIs.