In Spain it also related to planning permission. Once the building work has finished, you need to have the planning permission paper work in order. Therefore they often leave one small room unfinished (exposed on the outside wall) to claim work is still in progress.
I have lived all my life in Spain and that's not my experience. Maybe in some small rural towns you can (illegally) keep an unfinished work for years, as long as nobody notices.
However, that is absolutely not true for most Spanish cities.
