Banning of cryptocurency is never a joke and doesn't look like one as it does have its effect on the market. For example, if US was to banned Bitcoin today, the market will react very negatively and until another law is passed to contradict the ban, the market wouldn't recover. The government understand this and have been using it to their advantages which is why China bans Bitcoin related services in the industry in the past.
While we have people still making use of cryptocurency when they're banned in a country, it can't be compared to when cryptocurrency was welcomed in the country. Using your china example, even though 30 million users are using cryptocurrency, that number would had been in their thousands if millions of Bitcoin was welcomed by the government.