why don't you可以等于why not.那why doesn't he可以等于吗?为什么!

不行。Why not do sth?= Why don't you / we do sth?是针对you或we的建议,不针对他人。 再问： 那why doesn't he 有没有什么可以互换的 再答： Why doesn't he。。。不表示建议，是个特殊疑问句。