I'm afraid it probably applies especially to beginners. Look at it from the point of view of the judges. They see thousands of beginners each year and must judge them based on a few seconds of observation. If it were acceptable for beginners to ask judges for feedback, they would be overwhelmed by requests. And, in fact, they are not analyzing your dancing in depth, merely marking a comparative ranking of the dancers on the floor in each heat. Chances are, once your heat is over, they may not even remember the specifics of your dancing once they have marked down how they thought it compared to the others on the floor. And, frankly, I suspect a lot of them feel that it's not necessary for a beginner to have feedback from a top daancer/judge; any reasonably competent instructor can tell a beginner how to improve.
I know it's frustrating. The judging system is far from perfect, but it helps to remember that the placement you get at a comp is only a comparison to whoever else shows up that day to compete in your heats. And, if you asked all the judges who saw you, you'd get many different responses (I've had different judges mark the same dance as far apart as 3rd and 6th). You really need to depend on your own and your teacher's evaluation of how your dancing is improving. Seeing a video of your dancing will help(and you can also look at the other dancers in the background to see why they might have been marked higher).
Good luck with your dancing!