Answer:
Well the way we follow rules and distinct laws.
Step-by-step explanation:
Lets say were in a car. usually when we are driving, we find a sign that tells us to stop or names of streets that we can memorize to make it more simpler to give or receive directions. Though this would make a big change in society, we can always find a way to replace this change. Since we know by looking at a stop sign to stop because it says stop in white letters, though without the letters we can also assume it means stop since we have been born in a society that lets us know from a young age that red means stop. Also not all signs contain words, many signs when driving contain pictures instead of a written language. This makes it easier if you are from another country and don't know the language, to know what each sign means. Also people find it easier to receive information while going over 60mph as a image rather then words. So though a writing system is crucially important in society, there's always other ways to receive or give information other then a writing system.
Sorry for writing so much i just really enjoyed this question :D