One reason for not giving out a reason is that with the reasons given, collected and analyzed one could try to game the system by eliminating all signals that YC uses to detect bad applications without actually fixing the underlying issues.
There was a post lately about PG giving an interview and giving some shred of direction as to what makes YC reject applications and there was a big discussion on that fine point. He also said in the discussion that it was just a single way to discern between good and bad applications and that he doesn't give them all out so as not to be gamed around the indicators that YC uses to reject applications.
This is the explanation of pg that says his accent indicator is the only one he's willing to talk about. There was a long discussion and many posts and comments on several posts about this topic, and pg explained his position on the matter more deeply on: http://paulgraham.com/accents.html
Ah yes, thank you very much! Karma coming your way. I had read that essay and seen pg's comment. However, I didn't notice his implication that he wasn't willing to talk about most criteria because they could be faked/gamed. Kudos to you or whoever spotted that. However, I don't believe he said it was the only one he would discuss.
I am very sympathetic to their need to keep some of their cards private. While I and others might just be looking for a little constructive criticism for its own sake, no doubt there would be some who would try to use the information to portray themselves as something they are not or hide something that would hurt their chances. If this reduces the amount of feedback they could provide to a level where it wouldn't be helpful or makes it a complicated and risky affair, then it's reasonable to just avoid it altogether.
I am not sure why they wouldn't just say that though. Perhaps to avoid catalyzing attempts to identify and game their criteria?
Oh, I don't think its a matter of right or wrong. They have a right to decide whatever they think is best. I'm just trying to understand it.
You are right though, it is what it is. I suppose I am just interested in understanding why people do what they do, and this was an intriguing topic of personal relevance to me, and I assumed potentially to others here at this particular moment. But, I agree speculation on the topic is exhausted at this point. Thanks for humoring me anyways.
There was a post lately about PG giving an interview and giving some shred of direction as to what makes YC reject applications and there was a big discussion on that fine point. He also said in the discussion that it was just a single way to discern between good and bad applications and that he doesn't give them all out so as not to be gamed around the indicators that YC uses to reject applications.