With black cutting/trying to capture at c, as shown, white applies the same technique on the other side. Now there is a shortage of liberties situation which prevents black from cutting on this side.
White gets to connect whatever black tries, and the best black can do is get a couple of simple kos on top, but these are not life.
Attaching at is not so good. After , the result is a ko, not as good as a direct kill.