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?
For now, I would like to think that cryptocurrency adaptation is a sure thing that would happen, but what happened mid this year would definitely affect this adaptation greatly in a very negative way. Many people went bankrupted because of that great fall, and I think it would take time before the whole cryptocommunity could recover from such loss.