The problem with second chances is that they aren't first chances. This is not as trivial as it sounds: the difference between having no chance and a single chance is like the gulf between zero and one, or between nothing and something. But a second anything is just more something, a superfluity.
And then, having opened the door to superfluity, why not a third, or a fourth, or any nth chance? This is the difficult thing — the line between nothing and something is obvious, the line between something and something else is always less so. And that difference actually decreases the more you have of something; you can't see so clearly the difference between a 1,201st chance and a 1,202nd chance.