They were adopted because people no longer trusted the words of individual Aes Sedai. People still don't trust them. The Three Oaths failed.

There really won't be a need for the 3 Oaths, or The White Tower, once Tarmon Gaidon has finished - without the Dark One to give them a reason to unify channelers, the White Tower just becomes another political organization with members who combined are powerful enough to destroy any other nation that comes against them. Egwene is really going to have to reinvent the wheel in terms of a new mission for the White Tower, as a whole, if it is to survive. Otherwise, it might as well be retired or just lapse into an organization that trains and polices the actions of channelers.