Because when I go looking for who's to blame, I go looking for particular kinds of answers.
Because when I find who's to blame -- oddly enough, almost always somebody I already blame for something -- the emotional energy goes out of the question. I won't go looking for more. I've solved the whodunnit, come to the end of the narrative. Now's the time to relax with other people who also blame them, and think up sarcastic commentary.
Because when I stop there, I stop precisely at the verge of discovering something genuinely new. To wit -- what would my world have to look like, how would I have to understand it, what would I have to dread and desire in order to act as the people I'm blaming act? Until I reach that, not just intellectually, but with the heart, so that I'm spontaneously, unforcedly responding to them with compassion, I have solved nothing and understood nothing. Because the problem is not to identify who's at fault. The problem is to persuade them to do something else. And no one is ever persuaded of anything by someone who regards them as a villain. "Persuasion" in that case is is coercion. If you want to take that route, you'd better make sure you're faster and better-armed, more numerous and better organized, than the villains. Because you can confidently assume that they consider you to be to blame for the problem, for just as long a list of reasons, which they believe with just as much conviction.
Coercion is to my mind the last resort. Not only because I have conscientious objections to it, but because solutions resting on coercion are inherently unstable. They tend to come undone.
So that's why. Because to go looking for who's to blame is to go looking for coercive solutions.