Very few countries have banned all cryptocurrencies for payment.
I believe so few countries have banned crypto payments mostly because it's not used widely (thus my creating this thread!). It's not enough of a threat to worry about.
Now, I agree with you that, when crypto payments experience greater adoption, governments may ban certain cryptocurrencies for the reason you highlight... tax evasion. This is one of a series of regulations governments are concerned crypt payments evade.
That is why I think before a cryptocurrency will see widespread use is it needs to be "regulator friendly". I'm not aware any cryptocurrency that is "regulator friendly" because all cryptocurrencies hide the identity of the buyer & seller along with detail about what was purchased, where it was purchased, what, if any, taxes were paid, and so forth.