I don't think this is quite the argument you make it out to be, as we already have higher insurance premiums for smokers. Likewise, high-risk people are ineligible for organ transplants.

Really, anything can be a slippery slope if we want to look at it through that lens, but it's often not appropriate. This is one of those cases.

> people who take a car when they could take a bus, anyone who makes an unnecessary journey to do something that they benefit from such as church,

Some states sort of do this by requiring purchase of personal injury protection (PIP) from the auto insurer.