When i mentioned my brother was a Tornado pilot, my old section commander commented thus...Even though the North Koreans were bombed even more thoroughly than the Vietnamese would later be, their will to fight wasn't destroyed.
Airpower has very definite limits to what it can achieve, just like any other military tool.
"Any **** can press a button and drop a bomb from 10,000 ft, but you'll always need someone willing to follow up and deliver 9 inches of steel to the chest. That is the real test of courage".
It's not just air power. Look at Stallingrad. The germans basically flattened if over a prolonged period, yet still lost. And neigh on 250k civvies crawled out of their holes at the end.
Unless you go nuclear, litterally, you'll always still find opposition. People are like roaches in that respect and that's where the need for infantry comes in. Hard to argue with men intent on delivering up close and personal justice to the queens enemies!