Who is trusting the government with his own Bitcoin? I don't know about any people sending BTC to the government, so that the government could keep those BTC in a safe place.
There's no way to achieve 100% online security. This is a never ending battle between the hackers and the companies, that provide online security services. Even a cold wallet can get hacked. Some people trust third parties, because the third parties are promising them 100% guaranteed return of their crypto, even if the third party service gets hacked. I don't believe in such promises, but some people do believe in them.