why not
US /waɪ nɑt/
UK /waɪ nɑt/

1.
为什么不呢
used to suggest or agree to something
:
•
Let's go for a walk. Why not?
我们去散步吧。为什么不呢?
•
You want to try the new restaurant? Why not!
你想尝尝那家新餐馆吗?为什么不呢!
2.
为什么不呢, 原因是什么
used to ask for the reason why something is not happening or should not happen
:
•
You said you wouldn't go, but why not?
你说你不去,但为什么不呢?
•
They decided not to implement the new policy. Why not?
他们决定不实施新政策。为什么不呢?
: