If crypto does gain massive adoption and you are able to pay for things in crypto, there would be less of a reason for people to cash out into fiat. How would government collect taxes from crypto gains then? Also, if something like ETH becomes big, how is the government gonna stop people from making pyramids, ponzis, and scams in general?
There is no government who can stop PONZI, scam and pyramids.
It is on the people's hand, they know that the world is not safe though they are seeking for it.
They are being blind by big promises and fast money back. which is not good for them.
Even with out Cryptocurrency it is a big problem of the world and it will always to the people if they want to be one of the victims.