Why not和 Why don't的区别主要句型意思用法

Why not和Why don't都表达一种询问的口气,提建议的语气
Why not+do something Why don't+人称+do something
例句、Why not write it down 为什么不把它写下来呢?
Why don't you write it down 你为什么不把它写下来呢?