I always wish this too. At my previous job a (also at BigCorp) candidate reached out to ask why they hadn't been selected so I started putting together a little email for them trying to give polite feedback and encouraging them to apply again in a few years (they were great, but we needed a more senior role and had no open junior positions at that time). I asked my boss to review it and make sure it was okay, and he told me that under no circumstances do we ever give candidates feedback because if you say one wrong thing it's a lawsuit waiting to happen. Having been on the interview side where I really wanted to know how I could have done better, I was a bit angry on behalf of the candidate.