Why are archaeological finds important for studying those periods when writing already existed?

Because when writing existed, people could pass on to people from other generations how they lived, and what was important to them, and it is easier for people of our time to recognize what period of things they found.

One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.