Besides lack of any explicit policy / lack of time / legal risks, how does it really benefit the interviewers if they give such (probably unsolicited) feedback?

Besides lack of any explicit policy / lack of time / legal risks, how does it really benefit the interviewers if they give such (probably unsolicited) feedback? Most people are incapable of accepting criticism anyway, and nowadays where everyone blogs, tweets or posts on facebook, there is a risk that the interviewing company may have its hiring process tarnished just for giving constructive feedback in good faith. "No good deed goes unpunished".