OT saints believed in God and had to pay the tax. Now he is telling them that they don't need to pay the temple tax anymore. The Temple is going down. He has taken the keys of the kingdom from the Jews and given them to the Disciples and the Gentiles. It shows that Peter doesn't believe that what Jesus is here to do could have any effect on the present system.
Presumption can retard spiritual development and understanding.
It keeps me from appropriating the progressive revelation of God. We should avoid offending others. Our purpose being to make them more receptive to the gospel. Sometimes we need to avoid claiming our rights for the benefit of others. Certain things belong to the government and certain things belong to God.