This transparency is intended to prevent arbitrary, capricious, and thus ineffective regulation by inviting broad public participation and mandating a deliberate public debate over the content of proposed rules. One obvious purpose of this transparency is to provide clarity and predictability: it helps make clear how agencies are considering exercising their discretion.
The significant process protections in laws such as the APA are also meant to ensure fairness. The wisdom behind this approach is that fairness both helps bring forth more considered and effective regulations and builds respect for and adherence to the law, which is essential for enforcement. Transparency is central to our ability to assert that our rules are fair.