Yes, that's a pity. Sieges should be necessary. The single most important feature of the modern fortresses was to refuse the artillery a valuable target. Infantry could not attack the fort because the walls and first of all the ditch with its special defense facilities made it a nightmare. Scaling could be used but against determined defenders was near suicidal. Artillery could not break a fortress from the distance because the important structures, the fundamental walls opposite to the ditch could be only seen and reached with fire when you had arrived the top of the first glacis. So you had to destroy forward bastions and ravelines and bring your artillery near to the walls to create a breach. Otherwise your precious iron marbles were wasted in the fortresses earthen upper walls. All of this took a lot of time. This time and the inevitable fall of the fortress could be even calculated very properly in this new age of scientific siege warfare. The problem was that this time was often not available for the attacker.