Your are right, that a lot of cities are doing it regulary. The interessting point here is, that there are cities that have no sirens anymore due to the removal

Your are right, that a lot of cities are doing it regulary. The interessting point here is, that there are cities that have no sirens anymore due to the removal after the cold war. So such a nationwide test will help to check the efficiency and to modernize/rebuild the system where needed. //edit: same info was added to head comment.