In my country, the bank account is following by the government and if there is something unusual, the officer calls you for a meeting and ask you where this money come from.
If you transfer your money to your bank account when you sell your bitcoin, you have to pay the tax of the income. So bitcoin cannot kill the tax system.
Do you think that system really privacy for user? Nowadays, not like the era backward, most of the people know which system is better to keep safe their information and the privacy when using. The government do that just make the banking system become worse more in the opinion of the people. Until the people have enough power to change the monetary system, they will use other system to replace the banks.