why not to do sth对吗?waiting

why not 后接可直接接动词原形,意思是“为何不”,有建议意见的意思.
eg:1、He lives unhappy here ,why not let him go..他在这一点都不开心,何不让他走呢.
2、A:It's time for dinner.let's do some cakes to eat..吃饭时间到了,让我们做点蛋糕吃吧.
B:Oh,help me..We eat that yesterday..Why not have some vagetables I love it...哦.救救我吧.我们昨天才吃过.为什么不能吃点蔬菜呢.我喜欢蔬菜.
why not 还有些其他用法,可以参照资料学习.Hope that will help u..