You've echoed thoughts I've been having for a while now. I'm in Africa and when I look at how the government in my country handles its financial responsibility and then imagine a future where cryptocurrency rules, I see taxation as voluntary also, and not only that, but way more effective. I see that right now, people lose half their wages to tax, which gives back very little value to them. It's lost value that could have been better used to improve people's lives. This actually hampers everyone's growth and so you'll have the government taking tax from 10% of the population which happens to be working and that tax accounts for more than half of what they earn. It's a vicious non productive cycle.

Fast forward to when crypto rules and you'll see more people working more efficiently and paying taxes because they want to help their countries. Think 90% of the population being productive and earning very high values and then paying say 5% from that as tax. The government will end up getting more tax.

one more thing:

The government should be on the blockchain. Blockchain governance that's transparent and effective. Imagine a time when any citizen can just use an interface to see the current amount of tax money allocated to a certain department or cause and see the transactions being made clearly. That will actually motivate me to pay tax. When blockchain governance is in place we'll see a lot less people abusing their positions and 100% accountability.