In their whitepaper they said Bitcoin is useless if you cannot use it for tax payments:
"If governments refuse to accept cryptocurrencies for tax payments, the single most important transaction in an economy, that significantly reduces demand for cryptocurrencies. Governments are highly unlikely to ever take this step."
This quote is somewhat ironic, since Switzerland DOES allow their residents to pay municipal taxes with Bitcoin.
In my opinion, the use of Bitcoin is not just defined by the ability of paying taxes with it (which is apparently already happening) but also by the general use of shops adopting to it to buy goods and transfer money.
I firmly believe that Bitcoin will gain more use as we can imagine right now.
What do you think about it? Let me know in the comments.