It is not about
saving it is about
spending. You need to buy certain things in life, like food. You need to pay taxes if you do not want to be thrown in prison. You need to do business with people who need to buy things; barter will only get you so far.
So sure, you can have your offshore savings in whatever currency you want, but at some point you need to spend that money locally. Bitcoin does not avoid this in any way; it actually adds an additional step to transactions, since you need to convert Bitcoin into your local currency (even businesses that "accept Bitcoin" usually accept payments through services that exchange Bitcoin for some fiat currency for a small fee). You might dream of a world where Bitcoin never needs to be exchanged, but that is not going to happen until governments start accepting Bitcoin payments for tax purposes (and why would any government do that?).