Yeah, but taxing is much more fun if you can control every penny that is flowing somewhere. :)
I'm expecting a fully digital currency to replace all currencies we have now, and that probably world wide. It doesn't really matter if its bloch chain based or not. What matters is, that you cannot use it without going on record. No matter if its buying a bog roll, a TV or a house - your payment will be seen. And taxed, if thats so decided. That means, no more black work, no more sales without a bill, no more buying pot or anything else illegal. Total transparency of what people do, if it envolves money.
That's much better than just chasing after some taxes, that people even try to evade by all means, don't you agree?