I heard some left commentary on this issue that I think best sums up what we have seen with censorship from these companies: The government pressures private companies that own these platforms to establish private censorship guidelines to get around constitutional protections against censorship.
I think that currently the government is struggling to adapt their censorship regime to the new communications structure/technology brought on by the growth and evolution of the internet. They haven't got the new censorship regime completely down yet.
Also, isn't it the most neolib thing imaginable for the government to manage its censorship regime through what is essentially a web of public-private partnerships with companies like Google.