Honesty.
In short, if you expect honesty in a job search, you'll be disappointed.
We tell you why we didn't proceed and what we think you could do to make a difference if you choose to try again in a few years.
This is for our own benefit as much as the job seeker's. We don't want to leave a sour or even neutral taste in someone's mouth just because it didn't work out. Someone who is a bad fit now might be a good fit in the future, as they change or as we change, or we might be wrong that they are a bad fit now.