Hello Teachers

I know you have three ways to demand explanations.
[1] Why did Mr. Bush start the war in Iraq?
[2] Why is it that Mr. Bush started the war in Iraq?
[3] How come Mr. Bush started the war in Iraq?

Are there any differences in usage between three expressions?

Where Social Register (SR) 2.0 represents absolute neutrality,
SR[1] = 2.0
SR[2] = 2.5
SR[3] = 1.5

In my imagination, [2] shows a slightly more puzzled speaker than [1] and is uttered by an educated speaker on a serious television panel discussion, perhaps to a representative of the Bush administration, a speaker familiar with the background and implications of the questions.
[3] shows a less educated speaker or a child asking innocently about something as lowly as "How come the sky is blue?", a speaker who has much less of an idea of what he is even asking.

These characterizations are exaggerated to make what little of a point can be made about the differences!


Thank you for the quick and clear answer as usual. Your explanation is very informative and interesting. I am a bit amazed to know #2 can be more formal and more polite than #1.