Now the air is much worse than it used to be.之前为什么不要加what..

我认为 it 之前是应该加（或可以加）what 的,只不过很多时候都可以把它省略掉而已.换言之,在 it 之前加 what 或不加 what 都可以.
以下是从外国网页复制下来的两个例子：
例子一：
1a."You need to keep on using it and if you don’t,your skin will start to get even worse than what it was before." ［这句有 "what"］
1b."Your skin will get even more worse than it was before if you stop using (product xxx)." ［这句没有 "waht"］
例子二：
The cumulative Current Budget Deficit in March (€3,706 million) is over 40% worse than what it was at this time last year (€2,613 million).And for March alone the Current Budget Deficit is over 50% worse than it was in the same month last year.［第一句有 "what"；第二句没有 "what"］］