It's a cascade type of thing. Someone violates the ToS, the post gets reported, and it's decided that something has to be done to avoid yet another trainwreck. So, the offending post is taken out. But then someone has quoted that post. If that's left, the ToS violation is still visible. So that post needs to be taken out. And the post quoting that one again is meaningless now. Lather, rinse, repeat.
The Mod Corps could of course meticulously edit all those 2nd degree posts, but there are several good reasons for the current policy ("we don't edit posts; if it was deleted and you believe that the gist of it was within the ToS, rewrite and resubmit").
Yes, sometimes the baby gets thrown out with the bathwater. Stuff happens. Life isn't fair.