Why is it necessary to have an organizational chart?

Answer 1

It isn't necessary. Some companies function without them, in fact. However, having an organization of some sort, whether or not it is written down, is important. This helps people to know who to contact if they have a question, or helps people to know where to go up the "chain of command" if an issue needs to be escalated. Even in a family, it is helpful to know certain things... like who does what chore, so that three people aren't taking out the trash but refusing to do the dishes. Division of labor helps people to stay organized and get more done.