You said it. I just don't know why everyone replies this question.

你说的对，我只是不知道为什么大家都回复这个问题。

youdao

I don't know why you choose Chinese class?

我不知道为什么你们选择中文课？

youdao

I don't know the reason why you were absent from the meeting.

我不知道你为什么缺席会议。

youdao

What, you think I regret saving you? I can see that you do.I just... I don't know why.

VOA: standard.other

Some of you are probably going to be doctors and you don't know why I'm going to do special relativity or quantum mechanics, but you don't know when it will come in handy.

你们中的有些人可能会成为医生,但你们现在不能理解,我为什么要讲相对论和量子力学,但是说不定什么时候,你就用上了呢

耶鲁公开课 - 基础物理课程节选

And it makes you want to go get that insurance. I don't know why, but it does.

这让你想去买这家保险。我不知道为什么，但这就是这样。

广告泛滥 - SpeakingMax英语口语达人

Don't know why I ever thought I needed, don't know why I thought I needed, don't know why I ever thought I needed you.

NPR: Dustbin Bands: The Surreal McCoys

He said, yeah you, I don't know why you're running against George Bush.

NPR: Obama Challenges Bush Policies Backed By McCain

And then as I grew up, you know, I started to appreciate my culture and where they're from and so I decided, like you know, I don't like what's out there, so why don't I try doing something to change it too?

NPR: Rapping About Land and Identity