Real reason why China Banned Cryptocurrencies and Digital Currencies

I've been following stories around around why China has banned cryptocurrencies.

They could have stepped in and regulated ICOs, they could have regulated and taxed the exchanges, they could have stopped the flow out of the country and limited how cryptos were bought and spent. Instead the totally blocked the idea of decentralisation and not needing a governing body to control everything.

Check out this video from Julian at TenX who explains his idea around it so well.