Why does the IRS want bitcoins and what is it that they plan to do with all of these bitcoins?
I can understand taxing someone who converts BTC to USD. But why should BTC that remains BTC also be taxed?

I don't think BTC that remains BTC gets taxed. Of course, when you use BTC (which has appreciated in value) to buy something, a taxable event occurs. It is equivalent to you converting your BTC to USD and then using that USD to buy something. If you have capital gains which are realized, you are liable to pay tax. No escaping that!
