I could not understand why she felt compelled to behave so rudely to a friend.

我不能理解为什么她非要如此粗鲁地对待一位朋友。

《柯林斯英汉双解大词典》

What's baffled scientists for so long is "why is there a universe at all?".

让科学家们困惑了这么长时间的问题，是“为什么有宇宙？”。

youdao

No one has come up with a definitive answer as to why this should be so.

至于为什么该这样，还没有人给出明确的答复。

《柯林斯英汉双解大词典》

Why is the public still so interested in a woman who died so many years ago?

VOA: special.2009.12.06

And we'll talk about this more, so if this is not completely intuitive, we'll see why in a second.

关于这个我们将会讨论更多，所以如果这个不是完全凭直觉获知的，我们一会儿再来看看为什么。

麻省理工公开课 - 化学原理课程节选

I think the reason why triathlon is not so, so big is just because it requires a lot of time.

我认为铁人三项运动之所以不够普及，
是因为它需要大量的时间。

对体育项目的热爱 - SpeakingMax英语口语达人

So why a Web browser?

FORBES: Magazine Article

The NES, SNES, N64, Game Boy and DS were all big sellers in one way or another, so why would a product come along to give them so much trouble?

FORBES: The Only Problem with Nintendo's 3DS

So why ignore a figure capturing VeriSign's substantial distress, which will continue to affect the company?

FORBES: Magazine Article