Government is always abstracted in games, rather than being material. If a game had a tax collector, it would have to figure out what would happen if you killed the tax collector. What if the tax collector is actually a tax farmer[1]? Would his gang go after you? If the gang was too afraid of you, would they raise taxes on your neighbors to compensate?
[1] https://en.wikipedia.org/wiki/Farm_(revenue_leasing)