Remember Operation Anaconda in Afghanistan? The Army had no artillery in country and only limited attack helicopters--I think it was 8(?). As a result, we were unable to successfully suppress enemy fire upon the initial insertion and we lost helicopters and American lives. Further, fixed wing air by nature of its short loiter time, limited flexibility, and inability to work in bad weather was not able to provide the promised support to the ground troops, so when Taliban or Al Qaeda were spotted outside the range of infantry weapons, they often could not be engaged and most eventually got away. The reason for not having the heavy stuff was insufficient airlift.
More properly, there was no place to set the airlift down safely. No safe airfields. We had the birds.
Michael