The function of government is the exact opposite of private enterprise, yet the public only understands this in a crisis. Every time an electorate installs a successful businessman, the results are disastrous.
Regulations are only put in place when businesses failed to do so - at the expense of the commons. To roll them back in the name of efficiency is to fail the public that governments serve.
Lastly, businesses are only tasked with getting one product or service right. Governments are tasked with getting a system right. It's as if Musk is asking, "Why do we have the Fortune 500 when we could just have 1?"