Having been on the other side of that, there is a point. When an editor writes a rejection letter, aside from the fact that it already means what you wrote was better than 97% of what the editor saw that week, telling you why they turned it down isn't really quite the same level of feedback you get from an editor who has accepted a story and wants to get it over the proverbial finish line. A rejection letter is very broad strokes and first-impression. It's not actually editing. Editing needs a closer read, often a bit of back-and-forth with the author (I should say I learned a lot about editing in my younger days from both David Hartwell and Beth Meacham).