In this passage, Paul is answering the question of whether a Christian should, basically, do what they are told bu the governing authorithis, in this case The Roman Empire.
Paul said Yes, you must do what they tell you and he makes note about taxes ( probably because THAT was the main issue of the question he is answering).
Paul KNEW that rebillion is NOT a good thing for the emerging Christianity, so he nipped it in the bud, as he did with the slave issue.
To openly rebel against Rome was lead to persecutions and death, which is what ended up happening a few times over for various reasons, one imagines what would have happened of you add rebellion and inciting slaves to rebel to the list.
Paul knew that that best way to freedom was the famous "free your mind and the rest will follow", he knew that by "behaving" and doing what they were told ( in terms of following secular Law) that the christians would not only surive but expand and be allowed to preach.
Of course persecuations happened anyways.