I believe that the concept of "banning" people are afraid of is if their government would declare a law or something that prohibits banks, within their country, from exchanging Bitcoin  or any cryptocurrency to fiat. Yes people can still use Bitcoin and can transact via blockchain. But if these people cannot exchange their Bitcoin to cash, that would be troublesome. Bitcoin is still intangible and people does not have much trust in something like that so people would still lean on fiat.