It is also worth noting that every system has an architecture, even if this architecture is not formally documented or if the system is extremely simple and, say, consists of a single element. There is usually considerable value in documenting the architecture. Documented architectures tend to be more carefully considered -- and therefore, more effective -- than those that are not, since the process of recording the architecture naturally leads to thoughtful consideration.
Conversely, if an architecture is not documented, then it is difficult (if not impossible) to prove that it meets the stated requirements in terms of addressing qualities such as maintainability, accommodation of best practices, and so on. Architectures that are not documented, which appear to be the majority in existence today, tend to be accidental rather than intentional.