A: Penny, don't tell this to him yet, will you?
P: I don't see why not.
A: Well, it's better for Dan to tell him.
P: Why Dan? Why not me?.

A: 潘妮，还不要把这个告诉他好吗？
P: 我不懂为什么不能。
A: 让丹恩告诉他比较好。
P: 为何是丹恩？为什么不是我？

重点解说：

★ I don't see why not. = I don't see why I should not.