1. In this case, there's no opting out of personal protection without endangering innocents - as long as you're using public transportation infrastructure (i.e. roads), an unmaintained and/or uninsured car is a danger to others. There is public interest in ensuring such cars do not drive alongside regular traffic.

2. Such "protection" through enforcement of some minimal standards is a cost; if you remove that floor, the market will push straight down. What you intend as a voluntary opt-out mode will become involuntary, as prices adjusts to reflect the added costs of those standards. In other words, it's not just those who're willingly opting out that will be using "unprotected" services, but also those who can't afford the "protection" but need the service.

Point 2 can be also restated as: safety standards are a cost, the market will happily get rid of it (by externalizing them onto society at large) if you allow it to.