why worry?

Why worry?
解释：
Why did he leave?
Why turn off the gas?
Why not try again?
可以看到why后面都直接跟的动词助动词，中间不用加to，加了读着也别扭。尤其Why turn off the gas?这句，更是直接加了动词，足以证明应该是why worry.

Why to worry？ 语感告诉是这个

Why worry

应该是这个