We weren't there to experience it. A lot of the time, we use journals to learn parts of History. that doesn't mean it's exact information. We could never know whether it's true information or not. Since we're used to what we live in today, It could be hard for people to understand what happens in thd past, since their technology wasn't as advanced as it is today. Seeing the primary resources and technology that a time period uses definitely does show us the time period, or at least gives us a rough estimate.