We may not think very much about how people know what they know, but when we stop and do think about this, it is easy to see what a difference writing has made. Writing was a quantum leap for civilization. It saved people from having to reinvent the wheel, it allowed people to share ideas, facts, and great beauty through time and space, and it even aided commerce.
Imagine, if you will, a world without writing in which someone discovered an antibiotic a thousand years ago. There are bound to be rumors through the years about a discovery like this, but without the knowledge being written down, millions of people who could have been saved will die. We would all have to wait around for someone else to stumble upon this antibiotic again. There is no history of much of anything without writing. We would stumble around making the same mistakes over and over again, a sort of dreadful Fifty First Dates scenario in which we didn't know which tribes were historically our enemies and which were our friends or in which we did not know that those weeds we keep finding are actually edible and can save us from starvation. And whatever lessons we glean, with writing, we can transmit them to others and transmit them to the future, too.
Without writing, we would have little of the riches we have now in our lives. Philosophy has come down to us in writing. Our works of literature have come to us in writing. Beowulf probably emerged from an oral tradition, but had someone not written it down, it seems quite unlikely that we would be able to study and enjoy it today. Our appreciation for the heavens is thanks to ancient astronomers who wrote down what they knew. Music is handed down through the ages through writing now. We can look at scores of music that are hundreds of years old and play them. Mathematics is a form of writing, too, one that comes to us via Indian and Arabic cultures. Most of the religions in the world are based upon one or more holy texts that encouraged and solidified membership in their respective religious communities. And say what you will about the divisive aspect of religion, there is no question that its development has made substantial contributions to civilization, at the very least, creating community and building some of the most magnificent architecture ever built.
Writing helped commerce. People could create tallies, keep track of their inventories and profits, and take orders once we had writing. (Perhaps the first writing in commerce was a customer complaint!) Writing helped trade to expand, which spread civilization, as people went further afield and shared ideas. While I'm not sure that I would consider Amazon to be the quintessence of civilization, the fact is that it could not exist at all without writing.
There are probably hundreds more ways in which writing helped us to build civilization. It created a truly paradigmatic shift in the affairs of human beings. But certainly, at the very least, it saved us from having to invent or discover things over and over again, it allowed beauty and wisdom to be broadcast through time and space, and it was crucial in the development of trade and commerce.