Here you ask a rhetorical question.... if admitted students should decline the places they don't want to go to before or on April 15. And then follow up by suggesting that it is not their duty to do so . Are you alright, mate? Are you suggesting they should not? April 15 is the deadline and if people don't reject offers by then, as you suggest by asking the rhetorical question then that is really an unethical outlook. I mean it is basic decency and ethics... to decline an offer you know you are not taking up to give a chance to others who are on the waitlist. Stop being so mean.
Sorry but I say this as someone who has two offers (I do not want to flex but you have been condescending and disrespectful to waitlisted folks... painting then as some losers). I got two offers and got waitlisted at two other places. I hope to process from the waitlisted places as they are places I prefer more. But I have given up my second offer and only kept one offer in hand. I believe that is an ethical and PRACTICAL THING to do. I did so because I am super certain that between the two offers, I prefer one over the other. The original poster suggested people do the same and not keep offers of places they don't want to go to.
How is that wrong? Also, the margin between waitlisted and admitted is so small. So, it is so wrong on your part to be disrespectful to waitlisted applicants and to paint them as losers here.