Mind you, if government wants to impoverish people, bitcoin will neither make them rich. Assuming it's globally accepted as means of payment, you can only spend what you have.
They can not ban Bitcoin with a decentralized network and with private keys, Bitcoin users have control of their coins. Governments have no way to touch bitcoins owned by their citizens in non custodial wallets.
Do they want citizens to be rich?
I guess most governments want it, because with richer citizens, governments can tax more and earn more.
Are we now in support of Bitcoin just to evade paying taxes?
You can invade tax with Bitcoin until governments do more stricter regulations on tax policy. They will not let citizens to do money laundering, tax invasion through Bitcoin blockchain. Because governments want to milk money from citizens, and they will create laws and regulations for doing this effectively.
Citizens will want to do tax invasion but most of them will not succeed. I think obeying tax policy is good, because you can live a life without stress. If you are rich, I see no good reason to try tax invasion and live with stress and fear day by day.