Isnt a matter of their operational abilities but whether they are built to land on runways of such. These aircraft are built to land on asphalt or concrete runways. Not dirt, grass, or gravel. Doing such would damage the aircraft. Ice and snow are a little different as those are weather related phenomena that can happen on concrete and asphalt runways in the correct conditions. However, safe operations requires a cap on the amount that the aircraft can experience.
Some commercial aircraft are, in fact, able to land on ice runways, such as the 757 at airports in the Antarctic, yet this is a rare occurrence. Mainly due to the low wings. As you can tell, most military aircraft have a high wing base, which provide a larger distance between the ground and the wing structure, thus lowering damage rates to the wing in poor field conditions. That is why military aircraft are able to land at poorly maintained or built facilities. Commercial aircraft are not built for that purpose, and thus are more likely to be damaged by poorly maintained facilities.