Why should you be so suspicious?

你何必多疑？

《新英汉大辞典》

Why should you be so late today?

你今天怎么来的这么晚？

youdao

But why should you be here?

那你怎么会在这儿？

youdao

And this is line 679: Why should you be so cruel to yourself, And to those dainty limbs which nature lent For gentle usage and soft delicacy?

在第679行：，你为什么要对自己那么残忍，对于大自然赋予我们的四肢,只文雅的使用和温和的对待佳肴？

耶鲁公开课 - 弥尔顿课程节选

So why don't you tell me what the formal charge should be on the sulfur atom of thionyl chloride?

那么请大家来告诉我亚硫酰氯中,的硫原子应该有多少形式电荷？

麻省理工公开课 - 化学原理课程节选

Why should the amount by which you're attracted to the Earth be also a measure of how much you hate acceleration?

为什么物体受地球引力的大小,恰好能衡量物体加速的难易程度呢

耶鲁公开课 - 基础物理课程节选

Speaking of Dr. Oz, why should you be concerned about the infiltration of non-scientific medicine into our culture?

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With experts like this willing to help for free, why should you be the one to go it alone?

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And if you're special, why should you be self-conscious about being on-camera?

CNN: In Facebook age, is camera-shyness a thing of the past?