This is true, and I think BTC probably can only achieve a high dollar value if everyone starts using it. The more people that find use for it the higher the dollar value will be.
I think some things might change moving forward in the future for this to happen. If people realize that they do not have to pay income taxes if they get paid in BTC this might be a strong incentive for more people to want to get paid in BTC. The easier it becomes to pay for things with BTC the more people might use it. The most convent way I have seen people actually use BTC to pay for things is by loading BTC onto a prepaid credit card and use it just like any other card to fill their gas tanks or buy groceries ect.. but I think online shopping is where it will really thrive in the future. I think this will be a gradual change in the future as more people use it the volatility will gradually change also.
I live in the US and you are expected to pay taxes on your Bitcoin earnings. True, you may fly under the radar for your whole life. Much like people who work by getting paid under the table get away with it. However, if you get caught, prepare to have the government extract their pound of flesh from you. You can increase your chances by using an anonymous coin like XMR or ZEC. However, if you are buying goods and services or exchanging them for fiat, there is a good chance there will be a record of the transaction that isn't anonymous. I suppose you can uproot yourself and find a jurisdiction that won't tax you. However, how many people are really interested in moving to these jurisdictions? There is also going and living on a seastead.
If you buy or earn BTC and sell it for fiat you are suppose to pay tax on the profit even though the majority of people do not. If you earn BTC and pay for stuff in BTC how can this ever be taxed when it is not converted to fiat? BTC is only taxable when turned back into fiat. On top of that if you use a privacy coin like xmr, dash, ect. like you mentioned these are completely invisible on both ends of the transaction and there is almost nothing that can be done. Even if people used a non privacy based coin and everyone did it there is really nothing anyone can do to stop it. The manpower simply does not exist to handle a situation like this. It is like trying to stop the internet itself. A police officer can not stand on every corner in the world.
From any country in the world you can open a bitcoin wallet located on a computer in any other country in the world using a tor browser and send that bitcoin to a wallet on a computer in any other country in the world. It can not be stopped or regulated. It is the people that have the power not the governments. This is also exactly why bitcoin was created in the first place, to be an alternative way of doing things and give the financial power back to the people not banks, big business and governments.