Writing was very important in the development of civilization. Civilization is, of course, possible without writing, but writing makes it much easier. It does so because it allows people to keep records and it allows them to transmit and store information relatively easily.
Once a civilization reaches any really decent size, it needs a government. In order to function, governments need to tax the people they govern. Writing is very helpful for taxation purposes. If you know how to write, you can write down who has how much property and how much tax they have paid. You can have these records that allow you to make sure you collect all the taxes that are due. You can also write down laws so that people can easily remember what they are from generation to generation. Thus, writing is very helpful to governments, and governments are necessary for civilization.
Writing also helps develop civilization in other ways. Businesses can benefit from writing. They can keep records of who they have bought from and how much they have paid. They can keep records of who they have sold to and how much, if any, money is owed to them. Businesses, and people in general, can benefit from writing because writing can help them transmit and store information. Imagine that one business owner wants to make a deal with another. He can write a note to the other owner outlining the deal so the other owner can look it over and think about it. When the two of them agree, they can write out a contract. This contract stores the knowledge of what the deal was so they can both refer back to it and know exactly what they agreed to. People can also write other things down. They can write down ideas that they have had about science and technology. They can write out their religious scriptures. By doing these things, they make sure that they do not forget ideas that they have already had. This allows them to build their civilization as well.
In these ways, we can see that writing is very helpful in the development of a truly complex society. It helps allow government to exist and it makes it easier for people to do business and to pass down their laws, religious beliefs, and other ideas, thus helping to build their society.