The skill of explaining your work is a very important one in practically any creative problem solving field. This only increases as the technical complexity of the problems faced increases.

Sometimes this explaining happens in textual format, like code reviews and design specifications, but often it happens verbally. Absent an explanation, it's hard to build consensus among the parties involved (co-workers, users, management) that your solution (as manifested by the resulting code) is the right one, and for anything non-trivial, you surely can't expect others to just assume that it is the right one.