In general, if something is not visible, it won't provide the desired effect. Even the most advanced software, produced with the most cutting-edge technology, is entirely useless if the team that works on it is unable to understand it. All of the efforts applied by the team will be a waste of time.
Simply designing a software architecture isn't enough. It has to be shared with the whole team in a way that allows them to use it correctly when fulfilling their activities. The documentation made by the architects speaks for them today, when they should be doing things other than answering a hundred questions about software architecture, and it speaks for them tomorrow when they have left the project and someone else is in charge of its evolution and maintenance.
The second principle of the agile manifesto (http://agilemanifesto.org) is that "teams should...