Step 2: Buy stuff with bitcoins, possibly laundering them.

Step 3: Go to jail for intentional tax fraud. Good luck.

You need to spend those bitcoins to get some use of them - if you do it on a small scale, noone cares about losing 20 cents in tax; if you do it on a large scale, it becomes linked to you. For example - seller reports (for tax purposes) who/where they delivered goods; any bitcoin-money converter links your identity to this income; any bitcoin-vs-stuff barter can be a police sting operation, etc. Denying and laundering income is an old, traditional crime - and the same policing approaches that work with cash laundering will tend to work with bitcoin laundering as well.

Paying taxes costs some amount of money - but saying "good luck with that, tax man" can easily go over to crime/jail category; think twice if you want to go over to that road.