Because you're not expecting it.

因为你根本不会预计到。

youdao

I was not expecting it to work as it didn't have any of the "normal" ingredients I would think of helping to sleep (e. g. lavender).

我开始并没想到它会有效，因为它不含有“常见”的我以为会帮助睡眠的成份。

youdao

God sometimes breaks into our lives when we're not expecting it. God approaches us at times when we are not specifically asking for anything.

神时而在我们不经意时闯进我们的生命，有时会在我们并无特别所求时来到。

youdao

And I'm not expecting you to do that calculation here, because it involves the calculator, among maybe a piece of paper as well.

我并不期望你们去做这个计算,因为它需要一个计算器，也许还需要一张纸。

麻省理工公开课 - 化学原理课程节选

Now I'm not-- again, this is the kind of detail I'm not expecting you to remember, but it's just an exemplar of this broader issue about how dependence on certain foods leads to nutritional deficiencies that have to get remedied somehow or else people have health problems.

现在,我不是,我并不希望你们能记住这些细节,它们不过是作为一个例子来拓宽,由于依赖某种食物而导致营养不良的问题,要采取弥补措施,不然会引起健康问题

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

If you pass a function in C, a value that it's not expecting bad things happen and bad things generally reduce to segfault.

如果你在C中传递一个函数，一个没有预料的情况将会出现,这个情况通常是段错误。

哈佛公开课 - 计算机科学课程节选

"The ball is rarely involved in acute concussion -- if it is, it's when the ball hits someone in the head when they're not expecting it, " he told CNN.

CNN: Can playing football lead to brain damage?

While the filmmaker's sympathies clearly lie with her brainy, glamorous heroine in "Something's Gotta Give, " -- a movie that almost trips over its own cleverness during a table-turning climax set in Paris -- she declines to make Harry a complete fool. (Incomplete foolishness is funnier anyway.) "He's soulful when you're not expecting it, " Marin tells her mother.

WSJ: Keaton Turns Formula Into Feeling

We're not expecting to see it hit a flagship smartphone anytime soon, but it's nice to see Samsung has made a lot of progress on this front so far.

ENGADGET: CES 2013: Smartphones roundup Mobile