Sometimes, you use what's available. In some cases, the 'combat' vehicle may actually fit the niche; witness the amtracs in Houston last year.
Considering that Roebling's LVT-1 was intended for crossing swamps and shore for civilian purposes they great-grand children came back full circle to the original purpose.
In natural disaster situations AEV, ARV, AVLB and all the other big toys of especially the engineers have been used to help. But to write them into the requirements is silly. they are still tools of war for the battlefield. But the comfortable civilians want to be lied to I guess.