Because a) It would be boring and b) less tanks were knocked by airpower than claimed by the airforce. According to Niklas Zetterlings book Normady 1944 only about 7% of destroyed german tanks during the Normandy campaign (circa 1500 in total) can be said to have been knocked by airpower.
In Sledgehammer by Christopher Willbeck he explores the knocked Tigers during operation Goodwood. 13 were lost to airpower, 7 of them by high altitude carpet bombers before Goodwood began. Typhoons knocked 6 of them.
During the entire Operation goodwood the two airwings claimed some 390 knocked tanks. After the battle some 460 heavy German AFVs were standing knocked out on the battlefield, 300 were inspected. 10 had been knocked by airlaunched rockets. 3% of claimed became confirmed.
At Mortain the airforce of the allies claimed about 75 more kills than the germans had tanks.
Basically this myth about rockets from P-47s and Typhoons being the bane of German tankers is nothing more than a myth. AT-guns did the most of the damage both in the east and west.
There is your explanation, it doesn't make sense form a gameplay standpoint nor from an historical one.
While the rockets probably killed fewer tanks than claimed, that is the case for every service in the war, for both sides. It is certainly true that the German mobility suffered in good weather from air attacks, and their supply train, made up of trucks, rail, and horse, were quite vulnerable to air attack (as were infantry and lightly armored columns.)
Don't forget I mentioned horses. There were lots of horses. The vaunted, high tech, Wehrmacht supply chain was dependent on them.