Governments never legitimized bartering, trading, etc.

Because they're incredibly difficult to tax from a lack of a paper trail.

Make certain things illegal; if there's a motivation (illegal drug marked to cornered by the CIA, etc.).

Oh yeah. CIA's been making bank selling cocaine to other countries. Sometimes giving it away for free just to help destabilize others. I doubt they'd be okay with massive populations of their own citizens taking half their black-budget income.

They are probably in control of the major crypto groups.

Some they have 100% control over. Others they have enough control to cause major fluctuations in their favor, but they would lose that control instantly if a country opened the floodgates to normal citizens to use it for mundane transactions.

The independent ones might not be worth the effort at this point.

I'm not sure what you mean by that. Lack of notice doesn't always translate to a lack of worth.