Many government are seeing Bitcoin or cryptocurrency as a threat to their financial system and they think it should be regulated to solve the problem. Do you think they can regulate Bitcoin ?
I don't think that any government can regulate bitcoin alone, because they can't control Internet.
Only some kind of regulation on the world level is possible, but I doubt it will happen soon.
Governments can control income from bitcoin and crypto currencies when you decide to exchange your btc funds to the fiat money.
In the most countries, I believe, you will have ti report it and pay tax.