Security? Do you think security isn't flawed in cryptocurrency? Hmm, what if I tell you, Mt. Gox? Coindesk? Those exchanges were hacked and a lot of traders could be quitting that single day that it happened. Let's be honest that technologies aren't perfect and exploits will still exist regardless of how tight the security was in terms of how it is made. But exploits in such large part of the economy isn't to be tolerated. A lot of people will believe in technology, and they will expect that the technology they're interacting at would provide them the needs and one of those would be the security of what belongs to them.
For now, government wouldn't trust cryptocurrency. Some would but not in wholesome.