A government is accountable to all sorts of laws. A private entity only to some. There are entire branches of governments whose sole job is to make laws and decide what's wrong or right. Kicking the ball to companies is just intellectual laziness.
If we apply due process rules to this - we'd need a judge to sign off on every takedown which is very inefficient and probably stupid at best.
The recent government first amendment violation in San Francisco is an indication that the government still thinks it can do what it wants, we have a long way to go before any of us should trust it.