Think about how many transactions people do online each day? If Even little% to be taken... The government will be Strong because more money Exchanges more transactions means more Economic actvity and more Economic actvity the more government will get taxes.
With this I think you are talking about transparency and accountability. I think the whole transparency comes to corruption. A corrupt system will always find somehow to beat the system and this is bad for a nation. Even if it means not computing figures into blockchain , that can happen between two parties. Also where corruption thrives, even the figures reflected, the accuracies figures might not be given. Blockchain is good but it depends on the system to make it work