What most people do not understand, cryptocurrencies do only define the technology itself.

It does (and can) not define how it is used and also abused.

It is, eg. obvious that Bitcoin was made with the idea of representing a coin, a mean of payment. However, it is clear by now, that Bitcoin will never be a mean of payment. In contrast, it is mostly used as investment.

Also, you can not simply ban any cryptocurrency. The technology can not be 'stopped'. The lawmaker could only disallow it for this and that use.