Why not+动词原形。如：1.why not go to the park?2.Why not go out and see if there's some place we can dance?
Why not例句
I shrugged, as if to say, 'Why not?'
我耸了耸肩，仿佛在说，“为什么不？”
Why not?
有何不可？
Why not retrain for a job which will make you happier?
为什么不接受新的培训，找一份让你更快乐的工作？
Why not have it out with your critic, discuss the whole thing face to face?
为什么不和批评你的人讲个明白，面对面地把整件事情谈一谈呢？