Contextually, I have a couple of points as to why opening up accepted applications to the public is a bad idea.
1. New applicants can effectively take answers and make them their own i.e plagiarize previous - and succesful - applicants.
2. New applicants will look at accepted applications and know how to make a flawless app that won our support, rather than form an application from their own heart and brain.
Every new applicant should bring what they have to the table, not read over previous applicants' applications and take pages out of their books.
We want you to show us what you're about from a raw perspective, not see what the successful applicants did and learn from them, as that's ingenuine and doesn't paint a true picture of who you are as an applicant.
Making only the subforum, maybe, but that would conflict with my ideology above. Obviously, making the applications readable for the public is a complete no from me.
The reason as far as I'm aware for declined applications being open is so aspiring applicants can learn from them about what not to do/write in an application, declined applications generally do not give you the right answers, rather you have to disect them yourself to figure out the right things to say, that they must do themselves and not rely on studying the accepted applications.