I think it would be great if a company would tell you why they decided not to hire you, or why they decided to hire someone else instead.

That way you'd know if there was something about your qualifications that they didn't like, or if you said something problematic in your interview, or if it just came down to choosing among several equally-qualified candidates, and they chose the one that played softball because they needed more people on the company team.

Instead, we're usually left not knowing, which in my mind generally translates to imagining the worst then having to work at talking myself out of that interpretation.