The facade provides a simplified, standardized interface to a large set of objects. This avoids the problem of having to reference many different, complicated interfaces to each object of that set.
For example, if a program is currently undergoing revision, and a large number of objects have been created, then the facade is a convenience to the users of the program, who already have an abstract concept of what the program is doing for them. Thus, the programmers need design only the new features of the required program, using an interface (the facade) to the existing objects. This allows reuse of the existing objects without recoding. Work on implementing the facade can be separated from the work of implementing the new features.