There are at least three reasons why we would have government even if we were perfect. It is important to consider them. One of these reasons is that we would always have people, children to be exact, who need guidance. In a perfect world, we would still have children. Parents would still need to address them, substitute for their reason until they were capable of rule. Presumably also, it would take time to learn all the things needed to rule in any civil society, even of the perfect, so some temporary substitutional role for government, not rooted in disorder, might be conceived on a temporary basis, analogous to parental rule.
The two main reasons for government, however, would exist even if we lived in a perfect society. First we would still need to decide to stay together, to will our unity, to judge its reasonableness. If we saw that it would be well that we lived an organized life together, as we would, then we would still have in many cases a variety of good alternatives about what to do. Indeed, the more perfect we were, the more varied would be our choices, and therefore the more we would need an authority