You don't have to buy auto-insurance. If I lived and worked in Washington DC and didn't have any family living in the state, I wouldn't have it. I'd have public transportation, my bike, or a scooter to take me wherever I needed to go.
You only have teo buy auto-insurance if you're wanting to register a vehicle with the federal government to drive it on federally maintained roads.
In regards to the income tax, its been found constitutional by courts based on the fact that the constitution allows for the levying of taxes.