Why are many governments not regulating cryptocurrency?
Governments are unaware of the existence of cryptocurrencies and when they know about it, they have become popular and are trying to learn about it. But because cryptocurrency is beyond their control, they don't fully regulate it. Maybe they can only set policies to use cryptocurrencies and adapt it to the conditions in their country. It looks like the government is still studying it and allowing its people to use it. And hopefully, the government will continue to allow us to use it and not make regulations that are too strict for its citizens.
The government are not some kind of noob that doesn't know about the existence of cryptocurrency. They already knew it, remember they have different departments and intels that can gather information, but they have a more important task in their hands than giving notice to the cryptocurrency industry.
It is either they regulate or ban cryptocurrency, most prefer being in the middle because it won't cost them anything. The only time they get involved in crypto is when they see a threat or potential benefits they have on it.
Cryptocurrency is not rampant. There is no need for the government to regulate it. The government only regulates what it sees its citizen getting highly involved with.
A country will only regulate cryptocurrency when it sees the danger of how scammers using it to dupe its citizens.
I highly agree with you, the time when the government steps in are when a certain cryptocurrency had done huge damage to its citizen.