progressive prioritization

[Lexical]

The actual reason they don't completely obliterate the oil fields is because, when you are in the business of nation building, you want to keep as much infrastructure intact as possible. This allows a steady and more seemless transition back into normal life-styles without more than a hiccup especially when you are looking at toppling a power structure in less than a week. Quite simple really, do it quick enough for the common person not to feel the affects of war, and let business continue as usual.