Unfortunately, in my country you still have to pay taxes when you are cashing out your coins and also you cannot cash them all out you can only do in in a limit this way you have to pay a lot of taxes if you want to cash everything out.
That is, if you are going through the legal route. There are thousands of options out there to avoid taxes and it is up to you whether to use these methods or not. For example, you can order pre-paid Bitcoin debit cards from various service providers and withdraw fiat cash from the ATMs.
Yes I agree you don't need to be a saint and go through the legal route, all you need to avoid the platform that take your private details, like name, address or any legal documents. Say if you have your coins, on coinbase.com or electrum how in the world will your government find out you have coins, all you need to transfer it to someone abroad or here in the forum or local Bitcoin. Ways are many, if I wanted to pay taxes why would I use Bitcoins.