Because it works so well in Israel

[Anders Hallin]

U.S. levels houses of Iraqi insurgents

Pentagon officials rejected any comparison to the tactics employed by the Israeli military in the West bank and Gaza, saying the U.S. actions are not aimed at punishing sympathizers, but rather are aimed at eliminating legitimate military targets.

So the buildings destroyed by the Israeli aren't legitimate?

"Coalition forces are continuing to target any building that may be used by anti-coalition forces to plan attacks, produce weapons or harbor insurgents," a Pentagon spokesman told CNN.

Emphasis mine.
Sounds like a very controlled policy...

[Chris Nahr]

Technically, any building larger than a doghouse may be used to "to plan attacks, produce weapons or harbor insurgents"...

[Linoleum]

The million dollar question is whether the intelligence regarding the majority of buildings is coming from Iraqi sources.

There is a huge difference between swooping into a neighborhood and leveling a building versus having neighbors come and go 'um, can you do something about the bomb factory down the street?'

[Toddy]

Yet both methods are incredibly unreliable, especially in tribal societies where people will make up stories to get their rivals taken out. Look at what's happened in Afghanistan. Until the US got wise, it was bombing sites whenever somebody said "Hey, Taliban over here!"