what good is ...

(also what's the good of ...)

used to say that one does not think that something is helpful, useful, or worth doing by asking what the purpose of (doing) something is

通过问某人做某事的目的是什么，表达某人认为某事没有帮助、有用或不值得做

…有什么用

What good is sitting alone in your room?

一个人孤零零地在家坐着又有什么用?

What good does it do to bring an umbrella along if you are only going to leave it in the car?

如果你只是打算把伞放在车里，带伞又有什么用呢?