Why do scientists characterize society as a form of joint life activity of people?

This is very easy to explain. After all, in society, everyone depends on everyone. Let’s take a concrete example, a city, there are shops, hospitals, schools, kindergartens, cafes, restaurants and other facilities. It is clear that people work everywhere, everyone does his job, provides services to the whole society, but at the same time also uses the services that others provide. Thus, everyone depends on everyone, and this is the joint life activity of people, which forms society.