whatever is worth doing at all is worth doing (it) well.为什么 括号里的it 必须省略

问题描述:

whatever is worth doing at all is worth doing (it) well.为什么 括号里的it 必须省略

be worth doing 啊
this task -------- is worth dong well.加个名词或者指代不明的it才奇怪吧~