Looking at a map from my comfy armchair, it seems like a no brainer tactically and strategically to try and cut off and destroy the German salient after the German offensive in the Ardennes failed. German elite troops were exhausted, badly supplied and overextended, while Allied troops had been building on their flanks and had full air support. Cutting off and destroying the German spearhead would have turned the Battle of the Bulge from a German defeat into a German catastrophe, and deprived Germany of many of its remaining elite armored and mechanized formations

Instead, the Allies opted to simply push the German salient back into itself, battering through German defenses point blank all while allowing German units to escape with much of their equipment and personnel intact to fight another way