When you've become your planned '10-year self' and are running a company, you'll find that there is no up-side to giving a no-hire an honest reason for your decision and plenty of down-side for doing so. As an example here, the binary decision not to hire you as an employee has created such a grudge that, almost two years later, you're still bitter enough to compose a rant against the company -- even though you never set a foot inside the place!
How bad would your rant have been if you were told "you're just not strong in <certain knowledge you thought you had cased>" or "a colleague told us that you were exceptionally difficult to work with in high-pressure situations and often became bitter if you didn't get your way"? What would the up-side have been for the company telling you these things? Wouldn't your bad-mouthing have just become worse, with your rant here (and elsewhere?) even nastier?
Yes, it would be nice if we could all tell no-hires exactly what they need to work on, but it is a very rare person who would say "Thanks for the rejection! That's awesome feedback and I'll tell everyone how you've managed to make me a better developer!"