语法问题解答： “why don't you”后面通常跟动词的原形，构成“why don't you do sth.”的结构，用来提出建议或询问原因，意为“你为什么不……呢？”。
Why don't you后接什么
1、Why don't you，表示“为什么不”， 后接动词原形。
2、can't wait /can hardly wait 表示迫不及待，后接to do。
3、how about 后接动词ing形式，即how about doing？表示询问意见，“怎么样？”
具体用法如下：
1、why don't you do sth. 表示为什么不做某事。Why don't you，表示“为什么不”， 后接动词原形。如:
Why don't you have a cup of hot water？
为什么不喝一杯热水？
2、can't wait 表示迫不及待，后接to do。
I can hardly wait to see him again.
我迫不及待地想再次见到他.
3、how about 后接动词ing形式，how about doing表示“干什么，怎么样？”How about staying at Bart's overnight?在巴特家过夜, 你看怎么样?
Why don't you例句
1、Why don't you get yourself a car?
你为什么不买辆汽车呢？
2、Why don't you look in on me next time you're in town?
你下次进城顺便来看看我好吗？
3、Why don't you come over to England in the summer?
你为何不在夏天来英格兰呢？
4、You look hot ─ why don't you peel off?
你看来很热——为何不脱掉衣服？
5、It's very late now ─ why don't you sleep over?
现在已经很晚了——为什么不就睡这儿呢？